Document and Entity Information - USD ($)	12 Months Ended
Document and Entity Information - USD ($)	Dec. 31, 2015	Feb. 19, 2016	Jun. 30, 2015
Document And Entity Information [Abstract]
Document Type	10-K
Amendment Flag	false
Document Period End Date	Dec. 31, 2015
Document Fiscal Year Focus	2015
Document Fiscal Period Focus	FY
Trading Symbol	NKTR
Entity Registrant Name	NEKTAR THERAPEUTICS
Entity Central Index Key	0000906709
Current Fiscal Year End Date	--12-31
Entity Well-known Seasoned Issuer	Yes
Entity Current Reporting Status	Yes
Entity Voluntary Filers	No
Entity Filer Category	Large Accelerated Filer
Entity Common Stock, Shares Outstanding		135,939,051
Entity Public Float			$ 1,647,937,071

Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Current assets:
Cash and cash equivalents	$ 55,570	$ 12,365
Short-term investments	253,374	225,459
Accounts receivable, net of allowance of nil at December 31, 2015 and 2014	19,947	3,607
Inventory	11,346	12,952
Restricted cash	0	25,000
Other current assets	9,814	8,817
Total current assets	350,051	288,200
Property, plant and equipment, net	71,336	70,368
Goodwill	76,501	76,501
Other assets	4,173	6,552
Total assets	502,061	441,621
Current liabilities:
Accounts payable	2,363	2,703
Accrued compensation	5,998	5,749
Accrued clinical trial expenses	8,220	7,708
Other accrued expenses	4,156	6,418
Interest payable	4,198	6,917
Capital lease obligations, current portion	4,756	4,512
Deferred revenue, current portion	21,428	24,473
Other current liabilities	10,127	5,567
Total current liabilities	61,246	64,047
Senior secured notes, net	242,115	125,000
Capital lease obligations, less current portion	1,073	4,139
Liability related to the sale of future royalties	119,032	120,471
Deferred revenue, less current portion	62,426	76,911
Other long-term liabilities	9,740	14,721
Total liabilities	$ 495,632	$ 405,289
Commitments and contingencies
Stockholders’ equity:
Preferred stock, $0.0001 par value; 10,000 shares authorized; no shares designated, issued or outstanding at December 31, 2015 or 2014	$ 0	$ 0
Common stock, $0.0001 par value; 300,000 shares authorized; 135,289 shares and 131,216 shares issued and outstanding at December 31, 2015 and 2014, respectively	13	13
Capital in excess of par value	1,876,072	1,824,195
Accumulated other comprehensive loss	(2,170)	(1,567)
Accumulated deficit	(1,867,486)	(1,786,309)
Total stockholders’ equity	6,429	36,332
Total liabilities and stockholders’ equity	$ 502,061	$ 441,621

Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Statement Of Financial Position [Abstract]
Allowance for accounts receivable	$ 0	$ 0
Preferred stock, par value	$ 0.0001	$ 0.0001
Preferred stock, shares authorized	10,000,000	10,000,000
Preferred stock, shares designated	0	0
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0
Common stock, par value	$ 0.0001	$ 0.0001
Common stock, shares authorized	300,000,000	300,000,000
Common stock, shares issued	135,289,000	131,216,000
Common stock, shares outstanding	135,289,000	131,216,000

Consolidated Statements of Operations - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Revenue:
Product sales	$ 40,155	$ 25,152	$ 44,846
Royalty revenue	2,967	329	1,148
Non-cash royalty revenue related to sale of future royalties	22,058	21,937	22,055
License, collaboration and other revenue	165,604	153,289	80,872
Total revenue	230,784	200,707	148,921
Operating costs and expenses:
Cost of goods sold	34,102	28,533	38,509
Research and development	182,787	147,734	190,010
General and administrative	43,266	40,925	40,532
Total operating costs and expenses	260,155	217,192	269,051
Loss from operations	(29,371)	(16,485)	(120,130)
Non-operating income (expense):
Interest expense	(18,282)	(17,869)	(18,453)
Non-cash interest expense on liability related to sale of future royalties	(20,619)	(20,888)	(22,309)
Loss on extinguishment of debt	(14,079)	0	0
Interest income and other income (expense), net	1,680	814	1,124
Total non-operating expense, net	(51,300)	(37,943)	(39,638)
Loss before provision (benefit) for income taxes	(80,671)	(54,428)	(159,768)
Provision (benefit) for income taxes	506	(512)	2,245
Net loss	$ (81,177)	$ (53,916)	$ (162,013)
Basic and diluted net loss per share	$ (0.61)	$ (0.42)	$ (1.40)
Weighted average shares outstanding used in computing basic and diluted net loss per share	132,458	126,873	115,732

Consolidated Statements of Comprehensive Loss - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Statement Of Income And Comprehensive Income [Abstract]
Net loss	$ (81,177)	$ (53,916)	$ (162,013)
Other comprehensive income (loss):
Net unrealized loss on available-for-sale investments	(226)	(95)	(268)
Income tax provision on unrealized gain on available-for-sale investments	0	0	470
Net foreign currency translation loss	(377)	(291)	(1,026)
Other comprehensive loss, net of tax	(603)	(386)	(824)
Comprehensive loss	$ (81,780)	$ (54,302)	$ (162,837)

- Definition

The portion of profit or loss for the period, net of income taxes, which is attributable to the parent.

+ References + Details

Consolidated Statements of Stockholders' Equity (Deficit) - USD ($) shares in Thousands, $ in Thousands	Total	Common Shares [Member]	Capital in Excess of Par Value [Member]	Accumulated Other Comprehensive Income/(Loss) [Member]	Accumulated Deficit [Member]
Beginning Balance at Dec. 31, 2012	$ 47,018	$ 11	$ 1,617,744	$ (357)	$ (1,570,380)
Beginning Balance, Shares at Dec. 31, 2012		115,259
Shares issued under equity compensation plans	8,208	$ 0	8,208	0	0
Shares issued under equity compensation plans, Shares		1,235
Stock-based compensation	17,708	$ 0	17,708	0	0
Other comprehensive loss	(824)	0	0	(824)	0
Net loss	(162,013)	0	0	0	(162,013)
Ending Balance at Dec. 31, 2013	(89,903)	$ 11	1,643,660	(1,181)	(1,732,393)
Ending Balance, Shares at Dec. 31, 2013		116,494
Sale of common stock, net of issuance costs of $617	116,536	$ 1	116,535	0	0
Sale of common stock, Shares		9,775
Shares issued under equity compensation plans	46,984	$ 1	46,983	0	0
Shares issued under equity compensation plans, Shares		4,947
Stock-based compensation	17,017	$ 0	17,017	0	0
Other comprehensive loss	(386)	0	0	(386)	0
Net loss	(53,916)	0	0	0	(53,916)
Ending Balance at Dec. 31, 2014	36,332	$ 13	1,824,195	(1,567)	(1,786,309)
Ending Balance, Shares at Dec. 31, 2014		131,216
Shares issued under equity compensation plans	32,208	$ 0	32,208	0	0
Shares issued under equity compensation plans, Shares		4,073
Stock-based compensation	19,669	$ 0	19,669	0	0
Other comprehensive loss	(603)	0	0	(603)	0
Net loss	(81,177)	0	0	0	(81,177)
Ending Balance at Dec. 31, 2015	$ 6,429	$ 13	$ 1,876,072	$ (2,170)	$ (1,867,486)
Ending Balance, Shares at Dec. 31, 2015		135,289

Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Cash flows from operating activities:
Net loss	$ (81,177)	$ (53,916)	$ (162,013)
Adjustments to reconcile net loss to net cash used in operating activities:
Non-cash royalty revenue related to sale of future royalties	(22,058)	(21,937)	(22,055)
Non-cash interest expense on liability related to sale of future royalties	20,619	20,888	22,309
Stock-based compensation	19,669	17,017	17,708
Depreciation and amortization	12,855	12,927	14,275
Loss from redemption premium and incremental interest on 12% senior secured notes	12,500	0	0
Write-off of deferred financing costs on 12% senior secured notes	1,579	0	0
Other non-cash transactions	(2,365)	(560)	664
Changes in assets and liabilities:
Accounts receivable, net	(16,340)	(1,378)	3,576
Inventory	1,606	500	4,817
Other assets	(825)	(3,294)	6,423
Accounts payable	(412)	(6,359)	6,199
Accrued compensation	249	(8,505)	5,481
Accrued clinical trial expenses	512	(9,197)	(595)
Other accrued expenses	(2,278)	273	(1,915)
Interest payable	(2,719)	0	(166)
Deferred revenue	(17,530)	(4,664)	(12,399)
Liability related to receipt of refundable milestone payment	0	(70,000)	70,000
Other liabilities	3,032	(13,801)	9,164
Net cash used in operating activities	(73,083)	(142,006)	(38,527)
Cash flows from investing activities:
Purchases of investments	(297,608)	(297,251)	(268,068)
Maturities of investments	226,923	247,995	319,181
Sales of investments	42,544	21,661	2,887
Release of restricted cash	25,000	0	0
Purchases of property, plant and equipment	(11,195)	(9,976)	(4,091)
Net cash (used in) provided by investing activities	(14,336)	(37,571)	49,909
Cash flows from financing activities:
Payment of capital lease obligations	(5,187)	(3,536)	(2,992)
Proceeds from issuance of 7.75% senior secured notes, net of issuance costs	241,262	0	0
Repayment of 12% senior secured notes	(125,000)	0	0
Payment of redemption premium and incremental interest on 12% senior secured notes	(12,500)	0	0
Repayment of proceeds from sale of future royalties	0	(7,000)	(3,000)
Issuance of common stock, net of issuance costs	0	116,536	0
Proceeds from shares issued under equity compensation plans	32,208	46,984	8,208
Net cash provided by financing activities	130,783	152,984	2,216
Effect of exchange rates on cash and cash equivalents	(159)	(109)	32
Net increase (decrease) in cash and cash equivalents	43,205	(26,702)	13,630
Cash and cash equivalents at beginning of year	12,365	39,067	25,437
Cash and cash equivalents at end of year	55,570	12,365	39,067
Supplemental disclosure of cash flow information:
Cash paid for interest	20,225	17,445	17,590
Cash paid for income taxes	860	964	1,014
Supplemental schedule of non-cash investing and financing activities:
Property and equipment acquired through capital leases and other financing	$ 93	$ 5,231	$ 2,000

Organization and Summary of Significant Accounting Policies	12 Months Ended
	Dec. 31, 2015
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Organization and Summary of Significant Accounting Policies	Note 1 — Organization and Summary of Significant Accounting Policies Organization We are a biopharmaceutical company headquartered in San Francisco, California and incorporated in Delaware. We are developing a pipeline of drug candidates that utilize our PEGylation and advanced polymer conjugate technology platforms with the objective to improve the benefits of drugs for patients. Our research and development activities have required significant ongoing investment to date and are expected to continue to require significant investment. As a result, we expect to continue to incur substantial losses and negative cash flows from operations in the future. We have financed our operations primarily through cash generated from licensing, collaboration and manufacturing agreements and financing transactions. At December 31, 2015, we had approximately $308.9 million in cash and investments in marketable securities. Also, as of December 31, 2015, we had $255.8 million in debt, including $250.0 million in principal of senior secured notes (as further discussed in Note 5) and $5.8 million of capital lease obligations (Note 6), of which $4.8 million is current. Basis of Presentation, Principles of Consolidation and Use of Estimates Our consolidated financial statements include the financial position, results of operations and cash flows of our wholly-owned subsidiaries: Nektar Therapeutics (India) Private Limited (Nektar India) and Nektar Therapeutics UK Limited. All intercompany accounts and transactions have been eliminated in consolidation. Our consolidated financial statements are denominated in U.S. dollars. Accordingly, changes in exchange rates between the applicable foreign currency and the U.S. dollar will affect the translation of each foreign subsidiary’s financial results into U.S. dollars for purposes of reporting our consolidated financial results. Translation gains and losses are included in accumulated other comprehensive income (loss) in the stockholders’ equity (deficit) section of the balance sheet. To date, such cumulative translation adjustments have not been significant to our consolidated financial position. Aggregate gross foreign currency transaction gains (losses) recorded in operations for the years ended December 31, 2015, 2014, and 2013 were not significant. The preparation of consolidated financial statements in conformity with U.S. generally accepted accounting principles (GAAP) requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the consolidated financial statements and the reported amounts of revenue and expenses during the reporting period. Accounting estimates and assumptions are inherently uncertain. Actual results could differ materially from those estimates and assumptions. Our estimates include those related to estimated selling prices of deliverables in collaboration agreements, estimated periods of performance, the net realizable value of inventory, the impairment of investments, the impairment of goodwill and long-lived assets, contingencies, accrued clinical trial expenses, estimated non-cash royalty revenue and interest expense from our liability related to our sale of future royalties, stock-based compensation, and ongoing litigation, among other estimates. We base our estimates on historical experience and on other assumptions that management believes are reasonable under the circumstances. These estimates form the basis for making judgments about the carrying values of assets and liabilities when these values are not readily apparent from other sources. As appropriate, estimates are assessed each period and updated to reflect current information and any changes in estimates will generally be reflected in the period identified. Reclassifications Certain items previously reported in specific financial statement captions have been reclassified to conform to the current period presentation. Such reclassifications do not materially impact previously reported revenue, operating loss, net loss, total assets, liabilities or stockholders’ equity. Cash, Cash Equivalents, and Investments, and Fair Value of Financial Instruments We consider all investments in marketable securities with an original maturity of three months or less when purchased to be cash equivalents. Investments in securities with remaining maturities of less than one year, or where our intent is to use the investments to fund current operations or to make them available for current operations, are classified as short-term investments. Investments are designated as available-for-sale and are carried at fair value, with unrealized gains and losses reported in stockholders’ equity (deficit) as accumulated other comprehensive income (loss). The disclosed fair value related to our cash equivalents and investments is based primarily on the reported fair values in our period-end brokerage statements, which are based on market prices from a variety of industry standard data providers and generally represent quoted prices for similar assets in active markets or have been derived from observable market data. We independently validate these fair values using available market quotes and other information. Interest and dividends on securities classified as available-for-sale, as well as amortization of premiums and accretion of discounts to maturity, are included in interest income. Realized gains and losses and declines in value of available-for-sale securities judged to be other-than-temporary, if any, are included in other income (expense). The cost of securities sold is based on the specific identification method. Our cash, cash equivalents, and short-term investments are exposed to credit risk in the event of default by the third parties that hold or issue such assets. Our cash, cash equivalents, and short-term investments are held by financial institutions that management believes are of high credit quality and our investment policy limits investments to fixed income securities denominated and payable in U.S. dollars such as U.S. government obligations, money market instruments and funds, and corporate bonds and places restrictions on maturities and concentrations by type and issuer. Accounts Receivable and Significant Customer Concentrations Our customers are primarily pharmaceutical and biotechnology companies that are located in the U.S. and Europe. Our accounts receivable balance contains billed and unbilled trade receivables from product sales, milestones, other contingent payments and royalties, as well as time and materials based billings from collaborative research and development agreements. When appropriate, we provide for an allowance for doubtful accounts by reserving for specifically identified doubtful accounts. We generally do not require collateral from our customers. We perform a regular review of our customers’ payment histories and associated credit risk. We have not experienced significant credit losses from our accounts receivable. At December 31, 2015, three different customers represented 50%, 35%, and 10%, respectively, of our accounts receivable. At December 31, 2014, three different customers represented 40%, 31%, and 15%, respectively, of our accounts receivable. Inventory and Significant Supplier Concentrations Inventory is generally manufactured upon receipt of firm purchase orders from our collaboration partners. Inventory includes direct materials, direct labor, and manufacturing overhead and cost is determined on a first-in, first-out basis. Inventory is valued at the lower of cost or market and defective or excess inventory is written down to net realizable value based on historical experience or projected usage. Inventory related to our research and development activities is expensed when purchased. We are dependent on our suppliers and contract manufacturers to provide raw materials, drugs and devices of appropriate quality and reliability and to meet applicable contract and regulatory requirements. In certain cases, we rely on single sources of supply of one or more critical materials. Consequently, in the event that supplies are delayed or interrupted for any reason, our ability to develop and produce our drug candidates or our ability to meet our supply obligations could be significantly impaired, which could have a material adverse effect on our business, financial condition and results of operations. Long-Lived Assets Property, plant and equipment are stated at cost. Major improvements are capitalized, while maintenance and repairs are expensed when incurred. Manufacturing, laboratory and other equipment are depreciated using the straight-line method generally over estimated useful lives of three to ten years. Leasehold improvements and buildings recorded under capital leases are depreciated using the straight-line method over the shorter of the estimated useful life or the remaining term of the lease. Goodwill represents the excess of the price paid for another entity over the fair value of the assets acquired and liabilities assumed in a business combination. We are organized in one reporting unit and evaluate the goodwill for the Company as a whole. Goodwill has an indefinite useful life and is not amortized, but instead tested for impairment at least annually in the fourth quarter of each year using an October 1 measurement date. We assess the impairment of long-lived assets, primarily property, plant and equipment and goodwill, whenever events or changes in business circumstances indicate that the carrying amounts of the assets may not be fully recoverable. When such events occur, we determine whether there has been an impairment in value by comparing the carrying value of the asset with its fair value, as measured by the anticipated undiscounted net cash flows of the asset. In the case of goodwill impairment, market capitalization is generally used as the measure of fair value. If an impairment in value exists, the asset is written down to its estimated fair value. In March 2015, we announced that the primary endpoint for our BEACON Phase 3 clinical study for NKTR-102 as a single-agent therapy for women with advanced metastatic breast cancer did not achieve statistical significance. As a result, we performed an impairment analysis for our long-lived assets, including goodwill, as well as our primary long-lived asset group which is related to NKTR-102. Based on this analysis, we concluded that there is no impairment during the year ended December 31, 2015. Revenue Recognition Our revenue is derived from our arrangements with pharmaceutical and biotechnology collaboration partners and may result from one or more of the following: upfront and license fees, payments for contract research and development, milestone and other contingent payments, manufacturing and supply payments, and royalties. Our performance obligations under our collaborations may include licensing our intellectual property, manufacturing and supply obligations, and research and development obligations. In order to account for the multiple-element arrangements, we identify the deliverables included within the arrangement and evaluate which deliverables represent separate units of accounting. Analyzing the arrangement to identify deliverables requires the use of judgment, and each deliverable may be an obligation to deliver goods or services, a right or license to use an asset, or another performance obligation. Revenue is recognized separately for each identified unit of accounting when the basic revenue recognition criteria are met: there is persuasive evidence that an arrangement exists, delivery has occurred, the price is fixed or determinable, and collection is reasonably assured. At the inception of each new multiple-element arrangement or the material modification of an existing multiple-element arrangement, we allocate all consideration received under multiple-element arrangements to all units of accounting based on the relative selling price method, generally based on our best estimate of selling price (ESP). The objective of ESP is to determine the price at which we would transact a sale if the product or service was sold on a stand-alone basis. We determine ESP for the elements in our collaboration arrangements by considering multiple factors including, but not limited to, technical complexity of the performance obligation and similarity of elements to those performed under previous arrangements. Since we apply significant judgment in arriving at the ESPs, any material change in our estimates would significantly affect the allocation of the total consideration to the different elements of a multiple element arrangement. Product sales Product sales are primarily derived from fixed price and cost-plus manufacturing and supply agreements with our collaboration partners. We have not experienced any significant returns from our customers. Royalty revenue Generally, we are entitled to royalties from our collaboration partners based on the net sales of their approved drugs that are marketed and sold in one or more countries where we hold royalty rights. We recognize royalty revenue when the cash is received or when the royalty amount to be received is estimable and collection is reasonably assured. With respect to the non-cash royalties related to sale of future royalties described in Note 7, revenue is recognized when estimable, otherwise, revenue is recognized during the period in which the related royalty report is received, which generally occurs in the quarter after the applicable product sales are made. License, collaboration and other revenue The amount of upfront fees and other payments received by us in license and collaboration arrangements that are allocated to continuing performance obligations, such as manufacturing and supply obligations, are deferred and generally recognized ratably over our expected performance period under each respective arrangement. We make our best estimate of the period over which we expect to fulfill our performance obligations, which may include technology transfer assistance, research activities, clinical development activities, and manufacturing activities from development through the commercialization of the product. Given the uncertainties of these collaboration arrangements, significant judgment is required to determine the duration of the performance period and this estimate is periodically re-evaluated. Contingent consideration received from the achievement of a substantive milestone is recognized in its entirety in the period in which the milestone is achieved, which we believe is consistent with the substance of our performance under our various license and collaboration agreements. A milestone is defined as an event (i) that can only be achieved based in whole or in part either on the entity’s performance or on the occurrence of a specific outcome resulting from the entity’s performance, (ii) for which there is substantive uncertainty at the date the arrangement is entered into that the event will be achieved, and (iii) that would result in additional payments being due to the entity. A milestone is substantive if the consideration earned from the achievement of the milestone is consistent with our performance required to achieve the milestone or the increase in value to the collaboration resulting from our performance, relates solely to our past performance, and is reasonable relative to all of the other deliverables and payments within the arrangement. Our license and collaboration agreements with our partners provide for payments to us upon the achievement of development milestones, such as the completion of clinical trials or regulatory submissions, approvals by regulatory authorities, and commercial launches of drugs. Given the challenges inherent in developing and obtaining regulatory approval for drug products and in achieving commercial launches, there was substantial uncertainty whether any such milestones would be achieved at the time of execution of these licensing and collaboration agreements. In addition, we evaluated whether the development milestones met the remaining criteria to be considered substantive. As a result of our analysis, we consider our remaining development milestones under all of our license and collaboration agreements to be substantive and, accordingly, we expect to recognize as revenue future payments received from each milestone only if and as such milestone is achieved. Our license and collaboration agreements with certain partners also provide for contingent payments to us based solely upon the performance of the respective partner. For such contingent amounts, we expect to recognize the payments as revenue when earned under the applicable contract, which is generally upon completion of performance by the respective partner, provided that collection is reasonably assured. Our license and collaboration agreements with our partners also provide for payments to us upon the achievement of specified sales volumes of approved drugs. We consider these payments to be similar to royalty payments and we will recognize such sales-based payments upon achievement of such sales volumes, provided that collection is reasonably assured. Shipping and Handling Costs We recognize costs related to shipping and handling of product to customers in cost of goods sold. Research and Development Expense Research and development costs are expensed as incurred and include salaries, benefits and other operating costs such as outside services, supplies and allocated overhead costs. We perform research and development for our proprietary drug candidates and technology development and for certain third parties under collaboration agreements. For our proprietary drug candidates and our internal technology development programs, we invest our own funds without reimbursement from a third party. We record accruals for the estimated costs of our clinical trial activities performed by third parties. The financial terms of these agreements are subject to negotiation, vary from contract to contract and may result in uneven payment flows to our vendors. Payments under the contracts depend on factors such as the achievement of certain events, successful enrollment of patients, and completion of certain clinical trial activities. We generally accrue costs associated with the start-up and reporting phases of the clinical trials ratably over the estimated duration of the start-up and reporting phases. We generally accrue costs associated with the treatment phase of clinical trials based on the total estimated cost of the treatment phase on a per patient basis and we expense the per patient cost ratably over the estimated patient treatment period based on patient enrollment in the trials. In specific circumstances, such as for certain time-based costs, we recognize clinical trial expenses using a methodology that we consider to be more reflective of the timing of costs incurred. Advance payments for goods or services that will be used or rendered for future research and development activities are capitalized as prepaid expenses and recognized as expense as the related goods are delivered or the related services are performed. We base our estimates on the best information available at the time. However, additional information may become available to us which may allow us to make a more accurate estimate in future periods. In this event, we may be required to record adjustments to research and development expenses in future periods when the actual level of activity becomes more certain. Such increases or decreases in cost are generally considered to be changes in estimates and will be reflected in research and development expenses in the period identified. . Stock-Based Compensation Stock-based compensation arrangements include stock option grants and restricted stock unit (RSU) awards under our equity incentive plans, as well as shares issued under our Employee Stock Purchase Plan (ESPP), through which employees may purchase our common stock at a discount to the market price. We use the Black-Scholes option pricing model for the respective grant to determine the estimated fair value of the option on the date of grant (grant date fair value) and the estimated fair value of common stock purchased under the ESPP. The Black-Scholes option pricing model requires the input of highly subjective assumptions. These variables include, but are not limited to, our stock price volatility over the term of the awards, and actual and projected employee stock option exercise behaviors. Because our employee stock options have characteristics significantly different from those of traded options, and because changes in the subjective input assumptions can materially affect the fair value estimate, in management’s opinion, the existing models may not provide a reliable single measure of the fair value of our employee stock options or common stock purchased under the ESPP. Management will continue to assess the assumptions and methodologies used to calculate the estimated fair value of stock-based compensation. Circumstances may change and additional data may become available over time, which could result in changes to these assumptions and methodologies, and which could materially impact our fair value determination. We expense the value of the portion of the option or award that is ultimately expected to vest based on the historical forfeiture rate on a straight line basis over the requisite service periods in our Consolidated Statements of Operations. For awards that vest upon the achievement of performance milestones, we estimate the vesting period based on our evaluation of the probability of achievement of each respective milestone and the related estimated date of achievement. Stock-based compensation expense for purchases under the ESPP is recognized over the respective six-month purchase period. Expense amounts are recorded in cost of goods sold, research and development expense, and general and administrative expense based on the function of the applicable employee. Stock-based compensation charges are non-cash charges and as such have no impact on our reported cash flows. Net Loss Per Share Basic net loss per share is calculated based on the weighted-average number of common shares outstanding during the periods presented. For all periods presented in the Consolidated Statements of Operations, the net loss available to common stockholders is equal to the reported net loss. Basic and diluted net loss per share are the same due to our historical net losses and the requirement to exclude potentially dilutive securities which would have an anti-dilutive effect on net loss per share. During 2015, 2014 and 2013, potentially dilutive securities consisted of common shares underlying outstanding stock options and restricted stock unit awards (RSUs). There were weighted average outstanding stock options and RSUs of 21.1 million, 21.9 million and 20.7 million during the years ended December 31, 2015, 2014 and 2013, respectively. Income Taxes We account for income taxes under the liability method. Under this method, deferred tax assets and liabilities are determined based on differences between the financial reporting and tax reporting bases of assets and liabilities and are measured using enacted tax rates and laws that are expected to be in effect when the differences are expected to reverse. Realization of deferred tax assets is dependent upon future earnings, the timing and amount of which are uncertain. We record a valuation allowance against deferred tax assets to reduce their carrying value to an amount that is more likely than not to be realized. When we establish or reduce the valuation allowance related to the deferred tax assets, our provision for income taxes will increase or decrease, respectively, in the period such determination is made. We utilize a two-step approach to recognize and measure uncertain tax positions. The first step is to evaluate the tax position for recognition by determining if the weight of available evidence indicates that it is more likely than not that the position will be sustained upon tax authority examination, including resolution of related appeals or litigation processes, if any. The second step is to measure the tax benefit as the largest amount that is more than 50% likely of being realized upon ultimate settlement. Comprehensive loss Comprehensive loss is the change in stockholders’ equity (deficit) from transactions and other events and circumstances other than those resulting from investments by stockholders and distributions to stockholders. Our other comprehensive income (loss) is comprised of net loss, gains and losses from the foreign currency translation of the assets and liabilities of our India and UK subsidiaries, and unrealized gains and losses on investments in available-for-sale securities. Recent Accounting Pronouncements In May 2014, the Financial Accounting Standards Board (FASB) issued guidance codified in Accounting Standards Codification (ASC) 606, Revenue Recognition — Revenue from Contracts with Customers, which amends the guidance in former ASC 605, Revenue Recognition, and is effective for public companies for fiscal years beginning after December 15, 2017. Entities have the option of using either a full retrospective or a modified retrospective approach to adopt this new guidance. We are currently evaluating the impact of the provisions of ASC 606. In April 2015, the FASB issued guidance to simplify the presentation of debt issuance costs by requiring debt issuance costs to be presented as a deduction from the corresponding debt liability. This guidance is effective for our interim and annual periods beginning January 1, 2016 and early adoption is permitted. Upon adoption, the new guidance must be applied retrospectively to all periods presented. We do not believe the adoption of this guidance will have a material impact on our consolidated financial statements.

Cash and Investments in Marketable Securities

12 Months Ended

Dec. 31, 2015

Fair Value Disclosures [Abstract]

Cash and Investments in Marketable Securities

Note 2 — Cash and Investments in Marketable Securities

Cash and investments in marketable securities, including cash equivalents and restricted cash, are as follows (in thousands).

	Estimated Fair Value at
	December 31, 2015		December 31, 2014
Cash and cash equivalents	$	55,570	$	12,365
Short-term investments		253,374		225,459
Restricted cash		—		25,000
Total cash and investments in marketable securities	$	308,944	$	262,824

We invest in liquid, high quality debt securities. Our investments in debt securities are subject to interest rate risk. To minimize the exposure due to an adverse shift in interest rates, we invest in securities with maturities of two years or less and maintain a weighted average maturity of one year or less. As December 31, 2015 and 2014, all of our investments had maturities of one year or less.

Gross unrealized gains and losses were not significant at either December 31, 2015 or 2014. During the years ended December 31, 2015, 2014 and 2013, we sold available-for-sale securities totaling $42.5 million, $21.7 million, and $2.9 million, respectively, and realized gains and losses were not significant in any of those periods.

Restricted cash of $25.0 million was required to be maintained in a separate account until July 1, 2015 under the terms of our 12% senior secured notes due July 2017. This restriction expired on July 1, 2015 and the restricted funds were returned to us. Under the terms of our 7.75% senior secured notes due October 2020, we are required to maintain a minimum cash and investments in marketable securities balance of $60.0 million during the term of the notes.

Our portfolio of cash and investments in marketable securities includes (in thousands):

			Estimated Fair Value at
	Fair Value Hierarchy Level		December 31, 2015		December 31, 2014
Corporate notes and bonds		2	$	181,969	$	182,544
Corporate commercial paper		2		61,150		42,915
Obligations of U.S. government agencies		2		7,325		—
Available-for-sale investments				250,444		225,459
Money market funds		1		53,728		11,229
Certificate of deposit	N/A			2,930		—
Cash, including restricted cash	N/A			1,842		26,136
Total cash and investments in marketable securities			$	308,944	$	262,824

Level 1 —

Quoted prices in active markets for identical assets or liabilities.

Level 2 —

Inputs other than Level 1 that are observable, either directly or indirectly, such as quoted prices for similar assets or liabilities; quoted prices in markets that are not active; or other inputs that are observable or can be corroborated by observable market data for substantially the full term of the assets or liabilities.

Level 3 —

Unobservable inputs that are supported by little or no market activity and that are significant to the fair value of the assets or liabilities.

All of our investments are categorized as Level 1 or Level 2, as explained in the table above. During the years ended December 31, 2015, 2014 and 2013 there were no transfers between Level 1 and Level 2 of the fair value hierarchy.

At December 31, 2015 and 2014, we had letter of credit arrangements in favor of a landlord and certain vendors totaling $2.4 million. These letters of credit are secured by investments of similar amounts.

- Definition

The entire disclosure for the fair value of financial instruments (as defined), including financial assets and financial liabilities (collectively, as defined), and the measurements of those instruments as well as disclosures related to the fair value of non-financial assets and liabilities. Such disclosures about the financial instruments, assets, and liabilities would include: (1) the fair value of the required items together with their carrying amounts (as appropriate); (2) for items for which it is not practicable to estimate fair value, disclosure would include: (a) information pertinent to estimating fair value (including, carrying amount, effective interest rate, and maturity, and (b) the reasons why it is not practicable to estimate fair value; (3) significant concentrations of credit risk including: (a) information about the activity, region, or economic characteristics identifying a concentration, (b) the maximum amount of loss the entity is exposed to based on the gross fair value of the related item, (c) policy for requiring collateral or other security and information as to accessing such collateral or security, and (d) the nature and brief description of such collateral or security; (4) quantitative information about market risks and how such risks are managed; (5) for items measured on both a recurring and nonrecurring basis information regarding the inputs used to develop the fair value measurement; and (6) for items presented in the financial statement for which fair value measurement is elected: (a) information necessary to understand the reasons for the election, (b) discussion of the effect of fair value changes on earnings, (c) a description of [similar groups] items for which the election is made and the relation thereof to the balance sheet, the aggregate carrying value of items included in the balance sheet that are not eligible for the election; (7) all other required (as defined) and desired information.

+ References + Details

Inventory

12 Months Ended

Dec. 31, 2015

Inventory Disclosure [Abstract]

Inventory

Note 3 — Inventory

Inventory consists of the following (in thousands):

	December 31,
	2015		2014
Raw materials	$	3,236	$	2,200
Work-in-process		6,087		5,187
Finished goods		2,023		5,565
Total inventory	$	11,346	$	12,952

Property, Plant and Equipment

12 Months Ended

Dec. 31, 2015

Property Plant And Equipment [Abstract]

Property, Plant and Equipment

Note 4 — Property, Plant and Equipment

Property, plant and equipment consists of the following (in thousands):

	December 31,
	2015			2014
Building and leasehold improvements	$	77,665		$	72,228
Laboratory equipment		27,309			26,975
Manufacturing equipment		35,631			25,212
Furniture, fixtures and other equipment		24,987			23,451
Depreciable property, plant and equipment at cost		165,592			147,866
Less: accumulated depreciation		(102,712	)		(93,807	)
Depreciable property, plant and equipment, net		62,880			54,059
Construction-in-progress		8,456			16,309
Property, plant and equipment, net	$	71,336		$	70,368

Building and leasehold improvements include our manufacturing, research and development and administrative facilities and the related improvements to these facilities. Laboratory and manufacturing equipment include assets that support both our manufacturing and research and development efforts. Construction-in-progress includes assets being built to enhance our manufacturing and research and development efforts, including manufacturing equipment supporting our Amikacin Inhale program at third-party contract manufacturing locations in the U.S. and Germany. Under the terms of our arrangement with certain of these contract manufacturers, during the period the equipment is being constructed, we are obligated to pay for their costs incurred to date. As of December 31, 2015 and 2014, we have recorded a total of $4.3 million and $7.2 million, respectively, in other current and other long-term liabilities related to our obligation to purchase this equipment, which is recorded in property, plant and equipment. After the assets are placed into service, this liability is recorded as a capital lease liability and will be paid over approximately three years.

Depreciation expense, including depreciation of assets acquired through capital leases, for the years ended December 31, 2015, 2014, and 2013 was $11.4 million, $11.7 million, and $13.0 million, respectively.

Senior Secured Notes	12 Months Ended
Senior Secured Notes	Dec. 31, 2015
Debt Disclosure [Abstract]
Senior Secured Notes	Note 5 — Senior Secured Notes On September 30, 2015, we entered into a purchase agreement with TC Lending, LLC and TAO Fund, LLC for the sale of $250.0 million in aggregate principal amount of 7.75% senior secured notes due 2020 (the “Notes”). On October 5, 2015, we completed the sale and issuance of the Notes. The Notes are secured by a first-priority lien on substantially all of our assets. The Notes bear interest at a rate of 7.75% per annum payable in cash quarterly in arrears on January 15, April 15, July 15, and October 15 of each year, beginning on October 15, 2015. Interest is calculated based on actual days outstanding over a 360 day year. The Notes will mature on October 5, 2020, at which time the outstanding principal will be due and payable. In connection with the issuance of the Notes, we paid fees and expenses of $8.9 million, of which $8.3 million of transaction and facility fees paid directly to the purchasers of the Notes were capitalized as a debt discount and recorded as a reduction to the senior secured notes, net liability balance in our Consolidated Balance Sheet. An additional $0.4 million of direct issuance costs was capitalized and recorded in Other Assets in our Consolidated Balance Sheet and $0.2 million of fees were expensed. These debt discount and issuance costs will be amortized to interest expense over the five year term of the Notes. On October 5, 2015, we used a portion of the proceeds from the Notes to redeem the $125.0 million in aggregate principal amount of 12.0% senior secured notes due in 2017 (12% Notes). In addition, on October 5, 2015, we paid $3.3 million of accrued interest on the 12% Notes and made a $12.5 million redemption payment, which includes $1.2 million of additional interest paid to the note holders at redemption. As a result, we received $100.3 million in net proceeds in connection with these transactions. In addition, as a result of these transactions, in the year ended December 31, 2015, we recognized a $14.1 million loss on extinguishment of our 12% Notes, which consists of the $11.3 million redemption premium and $1.2 million of incremental interest paid to the note holders and the write-off of $1.6 million of unamortized issuance costs. The agreement, pursuant to which the Notes were issued, contains customary covenants, including covenants that limit or restrict our ability to incur liens, incur indebtedness, declare or pay dividends, redeem stock, issue preferred stock, make certain investments, merge or consolidate, make dispositions of assets, or enter into certain new businesses or transactions with affiliates, but do not contain covenants related to future financial performance. In particular, the Notes agreement requires us to maintain a minimum cash and investments in marketable securities balance of $60.0 million during the term of the Notes. The agreement also required that $50.0 million of the proceeds received from the issuance of the Notes be maintained in a restricted account until all liens securing the 12% Notes were released and all liens were released in November 2015 and the restrictions on this amount were removed. The Notes agreement provides that, beginning on October 5, 2017, we may redeem some or all of the Notes, subject to certain prepayment premiums and conditions. If we experience certain change of control events, the holders of the Notes will have the right to require us to purchase all or a portion of the Notes at a purchase price in cash equal to 101% of the principal amount thereof, plus accrued and unpaid interest to the date of purchase. In addition, upon certain asset sales, we may be required to offer to use the net proceeds thereof to purchase some of the Notes at 100% of the principal amount thereof, plus accrued and unpaid interest to the date of purchase. As of December 31, 2015, given that the Notes were recently issued in October 2015 and based on a discounted cash flow analysis using Level 3 inputs including financial discount rates, we believe the $250.0 million in principal amount of the Notes is consistent with its fair value.

Leases

12 Months Ended

Dec. 31, 2015

Leases [Abstract]

Leases

Note 6 — Leases

Capital Leases

We lease office space at 201 Industrial Road in San Carlos, California under a capital lease arrangement. Under the terms of the lease, rent increases up to 3% annually and the lease termination date is October 5, 2016. As of November 29, 2010, we ceased use of this space as a result of the relocation of our San Carlos operations and corporate headquarters to San Francisco, California. As of April 2013, we had subleased all of the San Carlos facility and our future minimum rental receipts under these subleases total $2.1 million as of December 31, 2015.

In addition to our San Carlos capital lease, we have purchased certain manufacturing equipment under capital leases. As of December 31, 2015 and 2014, the gross amount of assets recorded under capital leases was $5.1 million and $2.7 million, respectively, and the recorded value of these assets, net of depreciation, was $3.2 million and $1.2 million, respectively.

Future minimum payments for our capital leases at December 31, 2015 are as follows (in thousands):

Years ending December 31,
2016	$	5,135
2017		1,043
2018		72
Total minimum payments required		6,250
Less: amount representing interest		(421	)
Present value of future minimum lease payments		5,829
Less: current portion		(4,756	)
Capital lease obligation, less current portion	$	1,073

Operating Lease

On September 30, 2009, we entered into an operating sublease (Sublease) with Pfizer, Inc. for a 126,285 square foot facility located in San Francisco, California (Mission Bay Facility). Under the terms of the Sublease, we began making non-cancelable lease payments in 2014, after the expiration of our free rent period on August 1, 2014. The Sublease term is 114 months, commencing in August 2010 and terminating on January 31, 2020. Monthly base rent will escalate over the term of the sublease at various intervals. In addition, throughout the term of the Sublease, we are responsible for paying certain costs and expenses specified in the Sublease, including insurance costs and a pro rata share of operating expenses and applicable taxes for the Mission Bay Facility.

Our future minimum lease payments for our operating leases at December 31, 2015 are as follows (in thousands):

Years ending December 31,
2016	$	4,892
2017		5,037
2018		5,187
2019		5,344
2020		452
Total future minimum lease payments	$	20,912

We recognize rent expense on a straight-line basis over the lease period. For the years ended December 31, 2015, 2014, and 2013, rent expense for all of our operating leases, which primarily consists of our Mission Bay Facility, was approximately $3.2 million, $3.2 million, and $2.9 million, respectively. As of December 31, 2015 and 2014, we had total deferred rent balances of $8.5 million and $8.7 million, respectively, which are recorded in other current and other long-term liabilities in our Consolidated Balance Sheets.

Liability Related to the Sale of Future Royalties

12 Months Ended

Dec. 31, 2015

Note 7 — Liability Related to the Sale of Future Royalties

On February 24, 2012, we entered into a Purchase and Sale Agreement (the Purchase and Sale Agreement) with RPI Finance Trust (RPI), an affiliate of Royalty Pharma, pursuant to which we sold, and RPI purchased, our right to receive royalty payments (the Royalty Entitlement) arising from the worldwide net sales, from and after January 1, 2012, of (a) CIMZIA^®, under our license, manufacturing and supply agreement with UCB Pharma (UCB), and (b) MIRCERA^®, under our license, manufacturing and supply agreement with F. Hoffmann-La Roche Ltd and Hoffmann-La Roche Inc. (together referred to as Roche). We received aggregate cash proceeds of $124.0 million for the Royalty Entitlement. As part of this sale, we incurred approximately $4.4 million in transaction costs, which will be amortized to interest expense over the estimated life of the Purchase and Sale Agreement. Although we sold all of our rights to receive royalties from the CIMZIA^® and MIRCERA^® products, as a result of our ongoing manufacturing and supply obligations related to the generation of these royalties, we will continue to account for these royalties as revenue and recorded the $124.0 million in proceeds from this transaction as a liability (Royalty Obligation) that will be amortized using the interest method over the estimated life of the Purchase and Sale Agreement.

The following table shows the activity within the liability account during the year ended December 31, 2015 and for the period from the inception of the royalty transaction on February 24, 2012 (inception) to December 31, 2015 (in thousands):

	Year ended December 31, 2015			Period from inception to December 31, 2015
Liability related to the sale of future royalties—beginning balance	$	120,471		$	—
Proceeds from sale of future royalties		—			124,000
Payments from Nektar to RPI		—			(10,000	)
Non-cash CIMZIA^® and MIRCERA^® royalty revenue		(22,058	)		(76,841	)
Non-cash interest expense recognized		20,619			81,873
Liability related to the sale of future royalties – ending balance	$	119,032		$	119,032

Pursuant to the Purchase and Sale Agreement, in March 2014 and March 2013, we were required to pay RPI $7.0 million and $3.0 million, respectively, as a result of worldwide net sales of MIRCERA^® for the 12 month periods ended December 31, 2013 and 2012 not reaching certain minimum thresholds. The Purchase and Sale Agreement does not include any other potential payments related to minimum net sales thresholds and, therefore, we do not expect to make any further payments to RPI related to this agreement.

As a result of this liability accounting, even though the royalties from UCB and Roche are remitted directly to RPI, we will continue to recognize revenue for these royalties. During the years ended December 31, 2015, 2014 and 2013, we recognized $22.1 million, $21.9 million, and $22.1 million, respectively, in non-cash royalties from net sales of CIMZIA^® and MIRCERA^® and we recorded $20.6 million, $20.9 million and $22.3 million, respectively, of related non-cash interest expense.

As royalties are remitted to RPI from Roche and UCB, the balance of the Royalty Obligation will be effectively repaid over the life of the agreement. In order to determine the amortization of the Royalty Obligation, we are required to estimate the total amount of future royalty payments to be received by RPI and payments we are required to make to RPI as noted above over the life of the agreement. The sum of these amounts less the $124.0 million proceeds we received will be recorded as interest expense over the life of the Royalty Obligation. Since inception, our estimate of this total interest expense resulted in an effective annual interest rate of approximately 17%. We periodically assess the estimated royalty payments to RPI from UCB and Roche and to the extent the amount or timing of such payments is materially different than our original estimates, we will prospectively adjust the amortization of the Royalty Obligation. There are a number of factors that could materially affect the amount and timing of royalty payments from CIMZIA^® and MIRCERA^®, most of which are not within our control. Such factors include, but are not limited to, changing standards of care, the introduction of competing products, manufacturing or other delays, biosimilar competition, intellectual property matters, adverse events that result in governmental health authority imposed restrictions on the use of the drug products, significant changes in foreign exchange rates as the royalties remitted to RPI are made in U.S. dollars (USD) while significant portions of the underlying sales of CIMZIA^® and MIRCERA^® are made in currencies other than USD, and other events or circumstances that could result in reduced royalty payments from CIMZIA^® and MIRCERA^®, all of which would result in a reduction of non-cash royalty revenues and the non-cash interest expense over the life of the Royalty Obligation. Conversely, if sales of CIMZIA^® and MIRCERA^® are more than expected, the non-cash royalty revenues and the non-cash interest expense recorded by us would be greater over the term of the Royalty Obligation.

In addition, the Purchase and Sale Agreement grants RPI the right to receive certain reports and other information relating to the Royalty Entitlement and contains other representations and warranties, covenants and indemnification obligations that are customary for a transaction of this nature. To our knowledge, we are currently in compliance with these provisions of the Purchase and Sale Agreement; however, if we were to breach our obligations, we could be required to pay damages to RPI that are not limited to the purchase price we received in the sale transaction.

Commitments and Contingencies	12 Months Ended
Commitments and Contingencies	Dec. 31, 2015
Commitments And Contingencies Disclosure [Abstract]
Commitments and Contingencies	Note 8 — Commitments and Contingencies Royalty Expense We have third party licenses that require us to pay royalties based on our sales of certain products and/or on our recognition of royalty revenue under certain of our collaboration agreements. Royalty expense, which is reflected in cost of goods sold in our Consolidated Statements of Operations, was approximately $2.8 million, $3.4 million, and $4.1 million for the years ended December 31, 2015, 2014, and 2013, respectively. The overall maximum amount of these obligations is based upon sales of the applicable products by our collaboration partners and cannot be reasonably estimated. Purchase Commitments In the normal course of business, we enter into various firm purchase commitments related to contract manufacturing, clinical development and certain other items. As of December 31, 2015, these commitments were approximately $5.4 million, all of which are expected to be paid in 2016. Legal Matters From time to time, we are involved in lawsuits, arbitrations, claims, investigations and proceedings, consisting of intellectual property, commercial, employment and other matters, which arise in the ordinary course of business. We make provisions for liabilities when it is both probable that a liability has been incurred and the amount of the loss can be reasonably estimated. Such provisions are reviewed at least quarterly and adjusted to reflect the impact of settlement negotiations, judicial and administrative rulings, advice of legal counsel, and other information and events pertaining to a particular case. Litigation is inherently unpredictable. If any unfavorable ruling were to occur in any specific period, there exists the possibility of a material adverse impact on the results of our operations of that period and on our cash flows and liquidity. On August 14, 2015, Enzon, Inc. filed a breach of contract complaint in the Supreme Court of the State of New York (Court) claiming damages of $1.5 million (plus interest) for unpaid licensing fees through the date of the complaint. Enzon alleged that we failed to pay a post-patent expiration immunity fee related to one of the licenses. Following a hearing held on December 21, 2015, the Court granted Nektar’s motion to dismiss the Enzon complaint. Enzon has stated that it currently intends to appeal this dismissal. Foreign Operations We operate in a number of foreign countries. As a result, we are subject to numerous local laws and regulations that can result in claims made by foreign government agencies or other third parties that are often difficult to predict even after the application of good faith compliance efforts. Indemnification Obligations During the course of our normal operating activities, we have agreed to certain contingent indemnification obligations as further described below. The term of our indemnification obligations is generally perpetual. There is generally no limitation on the potential amount of future payments we could be required to make under these indemnification obligations. To date, we have not incurred significant costs to defend lawsuits or settle claims based on our indemnification obligations. If any of our indemnification obligations is triggered, we may incur substantial liabilities. Because the aggregate amount of any potential indemnification obligation is not a stated amount, the overall maximum amount of any such obligations cannot be reasonably estimated. No liabilities have been recorded for these obligations on our Consolidated Balance Sheets as of December 31, 2015 or 2014. Indemnifications in Connection with Commercial Agreements As part of our collaboration agreements with our partners related to the license, development, manufacture and supply of drugs based on our proprietary technologies and drug candidates, we generally agree to defend, indemnify and hold harmless our partners from and against third party liabilities arising out of the agreement, including product liability (with respect to our activities) and infringement of intellectual property to the extent the intellectual property is developed by us and licensed to our partners. As part of the sale of our royalty interest in the CIMZIA^® and MIRCERA^® products, we and RPI made representations and warranties and entered into certain covenants and ancillary agreements which are supported by indemnity obligations. Additionally, as part of our pulmonary asset sale to Novartis in 2008, we and Novartis made representations and warranties and entered into certain covenants and ancillary agreements which are supported by an indemnity obligation. In the event it is determined that we breached certain of the representations and warranties or covenants and agreements made by us in any such agreements, we could incur substantial indemnification liabilities depending on the timing, nature, and amount of any such claims. Indemnification of Underwriters and Initial Purchasers of our Securities In connection with our sale of equity and senior secured debt securities, we have agreed to defend, indemnify and hold harmless our underwriters or initial purchasers, as applicable, as well as certain related parties from and against certain liabilities, including liabilities under the Securities Act of 1933, as amended. Director and Officer Indemnifications As permitted under Delaware law, and as set forth in our Certificate of Incorporation and our Bylaws, we indemnify our directors, executive officers, other officers, employees, and other agents for certain events or occurrences that may arise while in such capacity. The maximum potential amount of future payments we could be required to make under this indemnification is unlimited; however, we have insurance policies that may limit our exposure and may enable us to recover a portion of any future amounts paid. Assuming the applicability of coverage, the willingness of the insurer to assume coverage, and subject to certain retention, loss limits and other policy provisions, we believe any obligations under this indemnification would not be material, other than an initial $1.5 million per incident for merger and acquisition related claims, $1.0 million per incident for securities related claims and $0.5 million per incident for non-securities related claims retention deductible per our insurance policy. However, no assurances can be given that the covering insurers will not attempt to dispute the validity, applicability, or amount of coverage without expensive litigation against these insurers, in which case we may incur substantial liabilities as a result of these indemnification obligations.

Stockholders' Equity

12 Months Ended

Dec. 31, 2015

Equity [Abstract]

Stockholders' Equity

Note 9 — Stockholders’ Equity

Preferred Stock

We have authorized 10,000,000 shares of Preferred Stock with each share having a par value of $0.0001. As of December 31, 2015 and 2014, no preferred shares are designated, issued or outstanding.

Common Stock

On January 28, 2014, we completed the issuance and sale of 9,775,000 shares of our common stock in a public offering with total proceeds of approximately $117.2 million after deducting the underwriting commissions and discounts of approximately $7.5 million. In addition, we incurred approximately $0.6 million in legal and accounting fees, filing fees, and other costs in connection with this offering.

Equity Compensation Plans

At December 31, 2015, we had 27,744,597 reserved shares of common stock, all of which are reserved for issuance under our equity compensation plans as summarized in the following table (share numbers in thousands):

Plan Category	Number of Securities to be Issued Upon Exercise of Outstanding Options & Vesting of RSUs (a)		Weighted- Average Exercise Price of Outstanding Options (b)		Number of Securities Remaining Available for Issuance Under Equity Compensation Plans (Excluding Securities Reflected in Column(a) (c)
Equity compensation plans approved by security holders(1)		18,056	$	11.33		7,657
Equity compensation plans not approved by security holders		2,032	$	10.30		—
Total		20,088	$	11.22		7,657

(1)	Includes shares of common stock available for future issuance under our ESPP as of December 31, 2015.

2012 Performance Incentive Plan

Our 2012 Performance Incentive Plan (2012 Plan) was adopted by the Board of Directors on April 4, 2012 and was approved by our stockholders on June 28, 2012. On the date of approval, any shares of our common stock that were available for issuance under all other previously existing stock plans (the 2008 Equity Incentive Plan, the 2000 Equity Incentive Plan, and the 2000 Non-Officer Equity Incentive Plan) became available for issuance under the 2012 Plan. In addition, 5,300,000 new shares were made available for award grants under the 2012 Plan. No new awards were granted under any of the previous stock plans after June 28, 2012. Any shares of common stock subject to outstanding awards under the previous stock plans that expire, are cancelled, or otherwise terminate at any time after December 31, 2011 are also available for award grant purposes under the 2012 Plan. On June 16, 2015, our stockholders approved an amendment to the 2012 Plan whereby 7,000,000 additional shares were made available for award grants under the 2012 Plan.

The purpose of the 2012 Plan and our other incentive plans is to attract, motivate, retain, and reward directors, officers, employees, and other eligible persons through the grant of awards and incentives for high levels of individual performance and increasing the value of our business, as well as to further align the interests of award recipients and our stockholders. The 2012 Plan authorizes stock options, stock appreciation rights, restricted stock, performance stock, stock units, stock bonuses, dividend equivalents, other similar rights to purchase or acquire shares, and other forms of awards granted or denominated in our common stock or units of the Company’s common stock, as well as cash bonus awards. Directors, officers, or employees, and certain consultants and advisors may receive awards under the 2012 Plan. Pursuant to the 2012 Plan, we granted or issued incentive stock options to officers and non-qualified stock options and RSUs to employees, officers, and non-employee directors. The requisite service period for stock options granted to our employees under the 2012 Plan as well as all other previously existing stock plans is generally four years; the requisite service period for stock options granted to our directors is generally one year. During the year ended December 31, 2015, we granted RSUs to employees, officers and non-employees directors. No RSUs were granted during 2014 or 2013. The requisite service period for RSUs granted under the 2012 Plan is generally three years for employees and one year for directors.

The maximum number of shares of our common stock that may be issued or transferred pursuant to awards under the 2012 Plan is 19,936,433 shares, plus any shares subject to outstanding awards under the previous stock plans that expire, are cancelled, or otherwise terminate for any reason. Generally, shares that are subject to or underlie awards which expire or for any reason are cancelled or terminated, are forfeited, fail to vest, or for any other reason (except for shares exchanged by a participant or withheld to pay the exercise price of an award granted and related tax withholding obligations) are not paid or delivered under the 2012 Plan will again be available for subsequent awards under the 2012 Plan. Shares issued in respect of any award, other than a stock option or stock appreciation right, granted under the 2012 Plan will be counted against the plan’s share limit as 1.5 shares for every one share actually issued in connection with the award.

The 2012 Plan will terminate on April 3, 2022, unless earlier terminated by the Board of Directors. The maximum term of a stock option or stock appreciation right under the 2012 Plan is eight years from the date of grant. The per share exercise price of an option generally may not be less than the fair market value of a share of the Company’s common stock on the NASDAQ Global Select Market on the date of grant.

Other Equity Incentive Plans

In addition to the 2012 Plan, we have other equity incentive plans under which options granted remain outstanding but no new options may be granted either as a result of the approval of the 2012 Plan or plan expiration. These plans include: (i) the 2008 Equity Incentive Plan (2008 Plan) which was adopted by the Board of Directors on March 20, 2008 and approved by our stockholders on June 6, 2008; (ii) the 2000 Equity Incentive Plan (2000 Plan) which was adopted by the Board of Directors on April 19, 2000 by amending and restating our 1994 Equity Incentive Plan, and which expired on February 9, 2010; and (iii) the 1998 Non-Officer Equity Incentive Plan which was adopted by our Board of Directors on August 18, 1998, and which was amended and restated in its entirety and renamed the 2000 Non-Officer Equity Incentive Plan on June 6, 2000 (2000 Non-Officer Plan).

Pursuant to the 2008 Plan and the 2000 Plan, we previously granted or issued incentive stock options to employees and officers and non-qualified stock options, rights to acquire restricted stock, restricted stock units, and stock bonuses to employees, officers, non-employee directors, and consultants. Pursuant to the 2000 Non-Officer Plan, we previously granted or issued non-qualified stock options, rights to acquire restricted stock and stock bonuses to employees and consultants who are neither officers nor directors of Nektar. The maximum term of a stock option under all of these plans is eight years.

Employee Stock Purchase Plan

In February 1994, our Board of Directors adopted the Employee Stock Purchase Plan (ESPP) pursuant to section 423(b) of the Internal Revenue Code of 1986. Under the ESPP, 2,500,000 shares of our common stock have been authorized for issuance. The terms of the ESPP provide eligible employees with the opportunity to acquire an ownership interest in Nektar through participation in a program of periodic payroll deductions for the purchase of our common stock. Employees may elect to enroll or re-enroll in the ESPP on a semi-annual basis. Stock is purchased at 85% of the lower of the closing price on the first day of the enrollment period or the last day of the enrollment period.

401(k) Retirement Plan

We sponsor a 401(k) retirement plan whereby eligible employees may elect to contribute up to the lesser of 60% of their annual compensation or the statutorily prescribed annual limit allowable under Internal Revenue Service regulations. The 401(k) plan permits us to make matching contributions on behalf of all participants, up to a maximum of $3,000 per participant. For the years ended December 31, 2015, 2014, and 2013, we recognized $0.9 million, $0.9 million, and $1.0 million, respectively, of compensation expense in connection with our 401(k) retirement plan.

Change in Control Severance Plan

On December 6, 2006, our Board of Directors approved a Change of Control Severance Benefit Plan (CIC Plan). This CIC Plan has subsequently been amended a number of times by our Board of Directors with the most recent amendment occurring on April 5, 2011. The CIC Plan is designed to make certain benefits available to our eligible employees in the event of a change of control of Nektar and, following such change of control, an employee’s employment with us or a successor company is terminated in certain specified circumstances. We adopted the CIC Plan to support the continuity of the business in the context of a change of control transaction. The CIC Plan was not adopted in contemplation of any specific change of control transaction.

Under the CIC Plan, in the event of a change of control of Nektar and a subsequent termination of employment initiated by us or a successor company other than for Cause (as defined in the CIC Plan) or initiated by the employee for a Good Reason Resignation (as defined in the CIC Plan) in each case within twelve months following a change of control transaction, (i) the Chief Executive Officer would be entitled to receive cash severance pay equal to 24 months base salary plus annual target incentive pay, the extension of employee benefits over this severance period and the full acceleration of unvested outstanding equity awards, and (ii) our Senior Vice Presidents and Vice Presidents (including Principal Fellows) would each be entitled to receive cash severance pay equal to twelve months base salary plus annual target incentive pay, the extension of employee benefits over this severance period and the full acceleration of unvested outstanding equity awards. In the event of a change of control of Nektar and a subsequent termination of employment initiated by the Company or a successor company other than for Cause within twelve months following a change of control transaction, all other employees would each be entitled to receive cash severance pay equal to 6 months base salary plus a pro-rata portion of annual target incentive pay, the extension of employee benefits over this severance period and the full acceleration of each such employee’s unvested outstanding equity awards. Under the CIC Plan, as amended, non-employee directors would also be entitled to full acceleration of vesting of all outstanding stock awards in the event of a change of control transaction.

- Definition

The entire disclosure for shareholders' equity comprised of portions attributable to the parent entity and noncontrolling interest, including other comprehensive income. Includes, but is not limited to, balances of common stock, preferred stock, additional paid-in capital, other capital and retained earnings, accumulated balance for each classification of other comprehensive income and amount of comprehensive income.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08.(d),(e))
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Reference 2: http://www.xbrl.org/2003/role/presentationRef
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Reference 3: http://www.xbrl.org/2003/role/presentationRef
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Reference 4: http://www.xbrl.org/2003/role/presentationRef
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Reference 5: http://www.xbrl.org/2003/role/presentationRef
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-Name Accounting Standards Codification
-Topic 210
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-Paragraph 1
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Reference 6: http://www.xbrl.org/2003/role/presentationRef
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Reference 7: http://www.xbrl.org/2003/role/presentationRef
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Reference 8: http://www.xbrl.org/2003/role/presentationRef
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Reference 9: http://www.xbrl.org/2003/role/presentationRef
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Reference 10: http://www.xbrl.org/2003/role/presentationRef
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-Name Accounting Standards Codification
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Reference 11: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
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Reference 12: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
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Reference 13: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
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-URI http://asc.fasb.org/extlink&oid=6928386&loc=d3e21564-112644

Reference 14: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Staff Accounting Bulletin (SAB)
-Number Topic 4
-Section E

Reference 15: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Staff Accounting Bulletin (SAB)
-Number Topic 4
-Section C

+ Details

License and Collaboration Agreements

12 Months Ended

Dec. 31, 2015

Organization Consolidation And Presentation Of Financial Statements [Abstract]

License and Collaboration Agreements

Note 10 — License and Collaboration Agreements

We have entered into various collaboration agreements including license agreements and collaborative research, development and commercialization agreements with various pharmaceutical and biotechnology companies. Under these collaboration arrangements, we are entitled to receive license fees, upfront payments, milestone and other contingent payments, royalties, sales milestones, and payments for the manufacture and supply of our proprietary PEGylation materials and/or reimbursement for research and development activities. All of our collaboration agreements are generally cancelable by our partners without significant financial penalty. Our costs of performing these services are generally included in research and development expense, except that costs for product sales to our collaboration partners are included in cost of goods sold.

In accordance with our collaboration agreements, we recognized license, collaboration and other revenue as follows (in thousands):

		Year Ended December 31,
Partner	Agreement	2015		2014		2013
AstraZeneca AB	MOVANTIK^TM (NKTR-118) and MOVANTIK^TM fixed-dose combination program (NKTR-119)	$	130,000	$	105,001	$	25,016
Roche	PEGASYS^® and MIRCERA^®		12,816		12,845		18,382
Baxalta Incorporated	ADYNOVATE^TM		10,694		10,258		1,702
Amgen, Inc.	Neulasta^®		5,000		5,000		5,035
Bayer Healthcare LLC	BAY41-6551 (Amikacin Inhale)		1,919		4,717		15,293
Affymax, Inc.	OMONTYS^®		—		—		7,149
Other			5,175		15,468		8,295
License, collaboration and other revenue		$	165,604	$	153,289	$	80,872

As of December 31, 2015, our collaboration agreements with partners included potential future payments for development milestones totaling approximately $113.3 million, including amounts from our agreements with Baxalta, Bayer and Ophthotech described below. In addition, we are entitled to receive the contingent development payments related to MOVANTIK^TM fixed-dose combination drug development programs and contingent sales milestone and royalty payments related to MOVANTIK^TM and the MOVANTIK^TM fixed-dose combination drug development programs as described below.

AstraZeneca AB: MOVANTIK^TM (naloxegol oxalate), previously referred to as naloxegol and NKTR-118, and MOVANTIK^TM fixed-dose combination program, previously referred to as NKTR-119

We are a party to an agreement with AstraZeneca AB (AstraZeneca) under which we granted AstraZeneca a worldwide, exclusive license under our patents and other intellectual property to develop, market, and sell MOVANTIK^TM and MOVANTIK^TM fixed-dose combination program. AstraZeneca is responsible for all research, development and commercialization and is responsible for all drug development and commercialization decisions for MOVANTIK^TM and the MOVANTIK^TM fixed-dose combination program. AstraZeneca paid us an upfront payment of $125.0 million, which we received in the fourth quarter of 2009 and which was fully recognized as of December 31, 2010. In addition, we have received the payments described further below based on development events related to MOVANTIK^TM completed solely by AstraZeneca. We are entitled to receive up to $75.0 million of commercial launch contingent payments related to the MOVANTIK^TM fixed-dose combination program, based on development events to be pursued and completed solely by AstraZeneca. In addition, we are entitled to significant and escalating double-digit royalty payments and sales milestone payments based on annual worldwide net sales of MOVANTIK^TM and MOVANTIK^TM fixed-dose combination products.

On September 16, 2014, the United States Food and Drug Administration (FDA) approved MOVANTIK^TM for the treatment of opioid-induced constipation (OIC) in adult patients with chronic, non-cancer pain. On December 9, 2014, AstraZeneca announced that MOVENTIG® has been granted Marketing Authorisation by the European Commission (EC) for the treatment of opioid-induced constipation (OIC) in adult patients who have had an inadequate response to laxative(s). As a result of the FDA’s approval, on September 16, 2014, we were entitled to a $35.0 million non-refundable payment from AstraZeneca, which was received in October 2014. In addition, the FDA’s approval of MOVANTIK^TM extinguished our contingent obligation to repay the $70.0 million payment made to us by AstraZeneca in November 2013 after the MOVANTIK^TM New Drug Application was accepted for review by the FDA. As a result, in September 2014, we fully recognized as revenue this $70.0 million payment.

On March 31, 2015, AstraZeneca announced that MOVANTIK™ launched in the United States which resulted in our receipt of a $100.0 million non-refundable commercial launch payment on March 31, 2015, which was recognized as revenue in March 2015. In March 2015, we agreed to pay AstraZeneca a total of $10.0 million to fund U.S. television advertising in consideration for certain additional commercial information rights. We recorded this $10.0 million obligation as a liability, and made the initial $5.0 million payment to AstraZeneca in July 2015. The remaining $5.0 million, which will be paid in July 2016, is included in other current liabilities in our Consolidated Balance Sheet at December 31, 2015. We determined that this $10.0 million obligation should be recorded as a reduction of revenue, which we recorded in the three months ended March 31, 2015. In August 2015, we received and recognized as revenue an additional $40.0 million non-refundable payment triggered by the first commercial sale of MOVENTIG® (the naloxegol brand name in the European Union or EU) in Germany. As of December 31, 2015, we do not have deferred revenue related to this agreement.

In general, other than as described above and in this paragraph, AstraZeneca has full responsibility for all research, development and commercialization costs under our license agreement. As part of its approval of MOVANTIK^TM, the FDA required AstraZeneca to perform a post-marketing, observational epidemiological study comparing MOVANTIK^TM to other treatments of OIC in patients with chronic, non-cancer pain. As a result, the royalty rate payable to us from net sales of MOVANTIK^TM in the U.S. by AstraZeneca will be reduced by up to two percentage points to fund 33% of the external costs incurred by AstraZeneca to fund such post approval study once it is initiated, subject to a $35.0 million aggregate cap. Any costs incurred by AstraZeneca can only be recovered by the reduction of the royalty paid to us. In no case can amounts be recovered by the reduction of a contingent payment due from AstraZeneca to us or through a payment from us to AstraZeneca.

Baxalta Incorporated: Hemophilia

We are a party to an exclusive research, development, license and manufacturing and supply agreement with Baxalta Incorporated (Baxalta) executed in September 2005 to develop products designed to improve therapies for Hemophilia A patients using our PEGylation technology. Under the terms of the agreement, we are entitled to research and development funding and are responsible for supplying Baxalta with its requirements for our proprietary materials. Baxalta is responsible for all clinical development, regulatory, and commercialization expenses. The agreement is terminable by the parties under customary conditions.

This Hemophilia A program includes ADYNOVATE^TM, which was approved by the FDA in November 2015 for use in adults and adolescents, aged 12 years and older, who have Hemophilia A and is now marketed in the U.S. As a result of the FDA’s approval, we achieved and recognized a $10.0 million development milestone in November 2015, which was included in the accounts receivable balance in our Consolidated Balance Sheet at December 31, 2015 and was received in January 2016. In August 2014, Baxalta announced positive top-line results from its Phase 3 pivotal clinical trial of ADYNOVATE^TM (previously referred to as BAX 855) which met the primary endpoint for the control and prevention of bleeding, routine prophylaxis and perioperative management for patients who were 12 years or older. As a result of this Phase 3 clinical trial meeting its primary endpoint, we earned development milestones totaling $8.0 million in September 2014. In addition, under the terms of this agreement, as of December 31, 2015, we are entitled to a $10.0 million development milestone due upon marketing authorization in the EU, as well as sales milestones upon achievement of annual sales targets and royalties based on annual worldwide net sales of products resulting from this agreement. As of December 31, 2015, we do not have significant deferred revenue related to this agreement.

Roche: PEGASYS® and MIRCERA^®

In February 1997, we entered into a license, manufacturing and supply agreement with Roche, under which we granted Roche a worldwide, exclusive license to certain intellectual property related to our proprietary PEGylation materials used in the manufacture and commercialization of PEGASYS^®. As a result of Roche exercising a license extension option in December 2009, Roche has the right to manufacture all of its requirements for our proprietary PEGylation materials for PEGASYS^® and we performed additional manufacturing, if any, only on an as-requested basis. In connection with Roche’s exercise of the license extension option in December 2009, we received a payment of $31.0 million. As of December 31, 2015, we no longer have any continuing performance obligations under this PEGASYS^® agreement and, therefore, have no deferred revenue related to this agreement.

In February 2012, we entered into a toll-manufacturing agreement with Roche under which we will manufacture the proprietary PEGylation material used by Roche to produce MIRCERA®. Roche entered into the toll-manufacturing agreement with the objective of establishing us as a secondary back-up supply source on a non-exclusive basis. Under the terms of our toll-manufacturing agreement, Roche paid us an upfront payment of $5.0 million and an additional $22.0 million in performance-based milestone payments upon our achievement of certain manufacturing readiness, validation and production milestones, including the delivery of specified quantities of PEGylation materials, all of which were completed as of January 2013. Roche will also pay us additional consideration for any future orders of the PEGylation materials for MIRCERA® beyond the initial quantities manufactured through January 2013. Roche has the right to terminate the toll-manufacturing agreement due to an uncured material default by us.

We analyzed the milestone payments under the agreement and determined that they did not meet the criteria for revenue recognition under the milestone method as a result of our continuing manufacturing obligations. We identified our back-up manufacturing obligation through December 2016 and the delivery of PEGylation materials specified in the agreement in 2012 and early 2013 as the units of accounting in the arrangement. We made our best estimate of the selling prices for these deliverables and allocated the total $27.0 million consideration to these items based on the relative selling price method. As of December 31, 2015, we have deferred revenue of approximately $5.4 million, which we expect to recognize through December 2016, the estimated end of our obligations under this agreement.

In August 2013, we agreed to deliver additional quantities of PEGylation materials used by Roche to produce PEGASYS® and MIRCERA®, all of which were delivered in the last quarter of 2013, for total consideration of $18.6 million. We determined that these incremental activities should be considered a material modification of the existing PEGASYS^® and MIRCERA® -related arrangements described above. As a result, we allocated the $18.6 million consideration to each of these arrangements and determined the amounts to be recognized or deferred based on the estimated selling prices of the undelivered obligations. As of December 31, 2015, we have deferred revenue of approximately $2.3 million related to these activities, which we expect to recognize through December 2016, the estimated end of our obligations under the modified arrangements.

Amgen, Inc.: Neulasta^®

In October 2010, we amended and restated an existing supply and license agreement by entering into a supply, dedicated suite and manufacturing guarantee agreement (the amended and restated agreement) and a license agreement with Amgen Inc. and Amgen Manufacturing, Limited (together referred to as Amgen). Under the terms of the amended and restated agreement, we guarantee the manufacture and supply of our proprietary PEGylation materials (Polymer Materials) to Amgen in an existing manufacturing suite to be used exclusively for the manufacture of Polymer Materials for Amgen (the Manufacturing Suite) in our manufacturing facility in Huntsville, Alabama (the Facility). This supply arrangement is on a non-exclusive basis (other than the use of the Manufacturing Suite and certain equipment) whereby we are free to manufacture and supply the Polymer Materials to any other third party and Amgen is free to procure the Polymer Materials from any other third party. Under the terms of the amended and restated agreement, we received a $50.0 million payment in the fourth quarter of 2010 in return for our guaranteeing the supply of certain quantities of Polymer Materials to Amgen including without limitation the Additional Rights described below and manufacturing fees that are calculated based on fixed and variable components applicable to the Polymer Materials ordered by Amgen and delivered by us. Amgen has no minimum purchase commitments. If quantities of the Polymer Materials ordered by Amgen exceed specified quantities, significant additional payments become payable to us in return for our guaranteeing the supply of additional quantities of the Polymer Materials.

The term of the amended and restated agreement ends on October 29, 2020. In the event we become subject to a bankruptcy or insolvency proceeding, we cease to own or control the Facility, we fail to manufacture and supply or certain other events, Amgen or its designated third party will have the right to elect, among certain other options, to take title to the dedicated equipment and access the Facility to operate the Manufacturing Suite solely for the purpose of manufacturing the Polymer Materials. Amgen may terminate the amended and restated agreement for convenience or due to an uncured material default by us. Our research facility in Huntsville, Alabama that we propose to sell is a different building and location from that of the Facility described here.

As of December 31, 2015, we have deferred revenue of approximately $24.2 million related to this agreement, which we expect to recognize through October 2020, the estimated end of our obligations under this agreement.

Bayer Healthcare LLC: BAY41-6551 (Amikacin Inhale)

In August 2007, we entered into a co-development, license and co-promotion agreement with Bayer Healthcare LLC (Bayer) to develop a specially-formulated inhaled Amikacin. We are responsible for development and manufacturing and supply of the nebulizer device included in the Amikacin product. Bayer is responsible for most future clinical development and commercialization costs, all activities to support worldwide regulatory filings, approvals and related activities, further development of Amikacin Inhale and final product packaging and distribution. In April 2013, Bayer initiated a Phase 3 clinical trial in the treatment of intubated and mechanically ventilated patients with Gram-negative pneumonia. As of December 31, 2015, we have received an upfront payment of $40.0 million (which was paid to us in 2007) and milestone payments totaling $30.0 million, including a $10.0 million development milestone which was achieved in 2013 as a result of the start of the Phase 3 clinical trial by Bayer. In addition, in June 2013, we made a $10.0 million payment to Bayer for the reimbursement of some of its costs of the Phase 3 clinical trial.

We are entitled to receive a total of up to an additional $50.0 million of development milestones upon achievement of certain development objectives, as well as sales milestones upon achievement of annual sales targets and royalties based on annual worldwide net sales of Amikacin Inhale. As of December 31, 2015, we have deferred revenue of approximately $19.3 million related to this agreement, which we expect to recognize through June 2029, the estimated end of our obligations under this agreement.

Ophthotech Corporation: Fovista^®

We are a party to an agreement with Ophthotech Corporation (Ophthotech), dated September 30, 2006, under which Ophthotech received a worldwide, exclusive license to certain of our proprietary PEGylation technology to develop, manufacture and sell Fovista®. Under the terms of our agreement, we are the exclusive supplier of all of Ophthotech’s clinical and commercial requirements for our proprietary PEGylation reagent used in Fovista®, which is currently in Phase 3 clinical development. On May 19, 2014, Ophthotech entered into a Licensing and Commercialization Agreement with Novartis Pharma AG for Fovista®. Under our agreement with Ophthotech, in June 2014, we received a $19.8 million payment in connection with this licensing agreement. As of December 31, 2015, we have deferred revenue of approximately $18.2 million related to this agreement, which we expect to recognize through March 2029, the estimated end of our obligations under our agreement with Ophthotech.

In addition, we are entitled to up to $9.5 million in additional payments based upon Ophthotech’s potential achievement of certain regulatory and sales milestones, including a $2.5 million milestone due upon acceptance for review of a regulatory approval application in the U.S. or EU. We are also entitled to royalties on net sales of Fovista® that vary based on sales levels, if commercialized.

Affymax, Inc.: OMONTYS^®

In April 2004, we entered into a license, manufacturing and supply agreement with Affymax, Inc. (Affymax) under which we provided Affymax with a worldwide, non-exclusive license under certain of our proprietary PEGylation technology to develop, manufacture and commercialize OMONTYS® (peginesatide). On February 23, 2013, Affymax and Takeda Pharmaceutical Company Limited announced a voluntary recall of all lots of OMONTYS® drug product as a result of new post-marketing reports regarding serious hypersensitivity reactions, including anaphylaxis, which can be life-threatening or fatal. In July 2013, Affymax terminated the license, manufacturing and supply agreement with Nektar.

We have received milestone and related payments under our agreement with Affymax and, as a result of the termination of our agreement with Affymax and our related performance obligations, we recognized the remaining $6.7 million of deferred revenue from this agreement in the year ended December 31, 2013.

Other

In addition, as of December 31, 2015, we have a number of collaboration agreements, including with our collaboration partner UCB, under which we are entitled to up to a total of $46.8 million of development milestones upon achievement of certain development objectives, as well as sales milestones upon achievement of annual sales targets and royalties based on net sales of commercialized products, if any. However, given the current phase of development of the potential products under these collaboration agreements, we cannot estimate the probability or timing of achieving these milestones. As of December 31, 2015, we have deferred revenue of approximately $14.5 million related to these other collaboration agreements, which we expect to recognize through 2020, the estimated end of our obligations under those agreements.

During the year ended December 31, 2014, two of our collaboration partners achieved the successful transfer of our commercial manufacturing process in connection with the PEGylation materials used in their products. In connection with our assistance with these manufacturing technology transfers, we received a total of $9.0 million of milestone payments. We concluded that these payments are substantive milestones and recognized them in their entirety in the year ended December 31, 2014.

Stock-Based Compensation

12 Months Ended

Dec. 31, 2015

Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]

Stock-Based Compensation

Note 11 — Stock-Based Compensation

We issue stock-based awards from our equity incentive plans, which are more fully described in Note 9. Stock-based compensation expense was recognized as follows (in thousands):

	Year Ended December 31,
	2015		2014		2013
Cost of goods sold	$	1,142	$	1,161	$	1,297
Research and development		9,207		7,528		7,910
General and administrative		9,320		8,328		8,501
Total stock-based compensation	$	19,669	$	17,017	$	17,708

As of December 31, 2015, total unrecognized compensation costs of $58.5 million related to unvested stock-based compensation arrangements are expected to be recognized as expense over a weighted-average period of 1.9 years.

Black-Scholes Assumptions

The following table lists the Black-Scholes option-pricing model assumptions used to calculate the fair value of employee and director stock options.

	Year Ended December 31,
	2015			2014			2013
Average risk-free interest rate		1.6	%		1.6	%		0.9	%
Dividend yield		0.0	%		0.0	%		0.0	%
Average volatility factor		50.8	%		51.6	%		61.2	%
Average weighted average expected life	5.3 years			5.2 years			5.2 years

The average risk-free interest rate is based on the U.S. treasury yield curve in effect at the time of grant for periods commensurate with the expected life of the stock-based award. We have never paid dividends, nor do we expect to pay dividends in the foreseeable future; therefore, we used a dividend yield of 0.0%. Our estimate of expected volatility is based on the daily historical trading data of our common stock at the time of grant over a historical period commensurate with the expected life of the stock-based award. For the years ended December 31, 2015, 2014, and 2013, we estimated the weighted-average expected life based on the contractual and vesting terms of the stock options, as well as historical cancellation and exercise data.

Stock-based compensation expense resulting from our ESPP was not material in the years ended December 31, 2015, 2014, and 2013.

Summary of Stock Option Activity

The table below presents a summary of stock option activity under our equity incentive plans (in thousands, except for price per share and contractual life information):

	Number of Shares			Weighted- Average Exercise Price per Share		Weighted- Average Remaining Contractual Life (in Years)		Aggregate Intrinsic Value(1)
Outstanding at December 31, 2014		21,995		$	10.50
Options granted		1,746			14.00
Options exercised		(3,937	)		7.89
Options forfeited & canceled		(1,022	)		13.42
Outstanding at December 31, 2015		18,782		$	11.22		4.67	$	105,830

Vested and expected to vest at December 31, 2015		18,360		$	11.14		4.62	$	104,749
Exercisable at December 31, 2015		12,222		$	9.89		3.60	$	85,074

(1)	Aggregate intrinsic value represents the difference between the exercise price of the option and the closing market price of our common stock on December 31, 2015.

The weighted-average grant-date fair value per share of options granted during the years ended December 31, 2015, 2014, and 2013 was $6.55, $6.50, and $4.95, respectively. The total intrinsic value of options exercised during the years ended December 31, 2015, 2014, and 2013 was $20.5 million, $25.9 million, and $4.5 million, respectively. The estimated fair value of options vested during the years ended December 31, 2015, 2014, and 2013 was $16.8 million, $15.2 million, and $14.1 million, respectively.

Summary of RSU Activity

During the year ended December 31, 2015, we granted RSUs to officers, employees and non-employee directors. No RSUs were granted in 2014 or 2013. Certain of the RSUs granted in 2015 vest upon achievement of pre-determined performance milestones, while the rest of the RSUs have a time-based vesting schedule. We expense the grant date fair value of the RSUs expected to vest ratably over the expected service or performance period.

A summary of RSU award activity is as follows (in thousands except for per share amounts):

	Units Issued		Weighted- Average Grant Date Fair Value		Aggregate Intrinsic Value(1)
Balance at December 31, 2014		—
Granted		1,306	$	15.30
Vested		—
Forfeited and canceled		—
Balance at December 31, 2015		1,306			$	22,012

(1)	Aggregate intrinsic value represents the difference between the grant price of the award and the closing market price of our common stock on December 31, 2015.

Income Taxes

12 Months Ended

Dec. 31, 2015

Income Tax Disclosure [Abstract]

Income Taxes

Note 12 — Income Taxes

Loss before provision (benefit) for income taxes includes the following components (in thousands):

	Year Ended December 31,
	2015			2014			2013
Domestic	$	(81,931	)	$	(56,414	)	$	(161,068	)
Foreign		1,260			1,986			1,300
Loss before provision (benefit) for income taxes	$	(80,671	)	$	(54,428	)	$	(159,768	)

Provision for Income Taxes

The provision (benefit) for income taxes consists of the following (in thousands):

	Year Ended December 31,
	2015			2014			2013
Current:
Federal	$	—		$	—		$	—
State		(1	)		1			1
Foreign		529			(482	)		1,838
Total Current		528			(481	)		1,839
Deferred:
Federal		—			—			422
State		—			—			49
Foreign		(22	)		(31	)		(65	)
Total Deferred		(22	)		(31	)		406
Provision (benefit) for income taxes	$	506		$	(512	)	$	2,245

The foreign benefit provision in the year ended December 31, 2014 is due to the reduction in taxes related to a favorable determination received from India proceedings.

Income tax provision related to continuing operations differs from the amount computed by applying the statutory income tax rate of 35% to pretax loss as follows (in thousands):

	Year Ended December 31,
	2015			2014			2013
U.S. federal provision (benefit)
At statutory rate	$	(28,235	)	$	(19,050	)	$	(55,919	)
State taxes		(1	)		1			50
Change in valuation allowance		22,210			11,831			55,042
Non-cash interest expense on liability related to sale of future royalties		7,217			7,311			7,808
Stock-based compensation		674			2,832			271
Foreign tax inclusion		1,773			—			—
Foreign tax differential		(7	)		(17	)		(20	)
Research credits		(4,529	)		(2,933	)		(6,273	)
Other		1,404			(487	)		1,286
Provision (benefit) for income taxes	$	506		$	(512	)	$	2,245

Deferred Tax Assets and Liabilities

Deferred income taxes reflect the net tax effects of loss and credit carryforwards and temporary differences between the carrying amount of assets and liabilities for financial reporting purposes and the amounts used for income tax purposes. Significant components of our deferred tax assets for federal and state income taxes are as follows (in thousands):

	December 31,
	2015			2014
Deferred tax assets:
Net operating loss carryforwards	$	447,761		$	423,776
Research and other credits		70,258			66,666
Deferred revenue		29,658			29,758
Stock-based compensation		22,832			21,948
Capitalized research expenses		12,440			14,795
Sale of future royalties		12,319			20,153
Reserves and accruals		8,309			8,288
Property, plant and equipment		6,451			8,264
Other		3,158			2,218
Deferred tax assets before valuation allowance		613,186			595,866
Valuation allowance for deferred tax assets		(612,996	)		(595,690	)
Total deferred tax assets		190			176
Total deferred tax liabilities		—			—
Net deferred tax assets	$	190		$	176

Realization of our deferred tax assets is dependent upon future earnings, if any, the timing and amount of which are uncertain. Because of our lack of U.S. earnings history, the net U.S. deferred tax assets have been fully offset by a valuation allowance. The valuation allowance increased by $17.3 million and $9.7 million during the years ended December 31, 2015 and 2014, respectively. The valuation allowance includes approximately $35.6 million of income tax benefit at both December 31, 2015 and December 31, 2014 related to stock-based compensation and exercises prior to the implementation of the accounting guidance for stock-based compensation that will be credited to additional paid in capital when realized.

Undistributed earnings of our foreign subsidiary in India are considered to be permanently reinvested and accordingly, no deferred U.S. income taxes have been provided thereon. Upon distribution of those earnings in the form of dividends or otherwise, we would be subject to U.S. income tax. As of December 31, 2015, U.S. income taxes have not been provided on a cumulative total of $4.4 million of such earnings. Any incremental tax liability would be insignificant due to foreign tax credits that would be realized upon distribution.

Net Operating Loss and Tax Credit Carryforwards

As of December 31, 2015, we had a net operating loss carryforward for federal income tax purposes of approximately $1,223.6 million, portions of which will begin to expire in 2018. As of December 31, 2015, we had a total state net operating loss carryforward of approximately $489.6 million, portions of which will begin to expire in 2016. Utilization of some of the federal and state net operating loss and credit carryforwards are subject to annual limitations due to the “change in ownership” provisions of the Internal Revenue Code of 1986 and similar state provisions.

We have federal research credits of approximately $45.0 million, which will begin to expire in 2019 and state research credits of approximately $24.6 million which have no expiration date. We have federal orphan drug credits of $17.7 million which will begin to expire in 2026. These tax credits are subject to the same limitations discussed above.

Unrecognized tax benefits

We have incurred net operating losses since inception. Our policy is to include interest and penalties related to unrecognized tax benefits, if any, within the provision for income taxes in the consolidated statements of operations. If we are eventually able to recognize our uncertain positions, our effective tax rate may be reduced. We currently have a full valuation allowance against our U.S. net deferred tax asset which would impact the timing of the effective tax rate benefit should any of these uncertain tax positions be favorably settled in the future. Any adjustments to our uncertain tax positions would result in an adjustment of our net operating loss or tax credit carry forwards rather than resulting in a cash outlay. The decrease in the unrecognized tax benefits primarily relates to a recent California Supreme Court decision relating to the calculation of apportionment of income.

We file income tax returns in the U.S., California, Alabama, and India. Because of net operating losses and research credit carryovers, substantially all of our domestic tax years remain open and subject to examination. We are currently under examination in India for the fiscal years ending 2009 through 2015.

We have the following activity relating to unrecognized tax benefits (in thousands):

	December 31,
	2015			2014			2013
Beginning balance	$	27,522		$	16,363		$	14,067
Tax positions related to current year
Additions:
Federal		529			502			477
State		443			6,141			381
Reductions		—			—			—
Tax positions related to prior year
Additions:
Federal		—			—			636
State		—			5,258			—
Foreign		—			—			802
Reductions		(11,110	)		(742	)		—
Settlements		—			—			—
Lapses in statute of limitations		—			—			—
Ending balance	$	17,384		$	27,522		$	16,363

Although it is reasonably possible that certain unrecognized tax benefits may increase or decrease within the next twelve months, we do not anticipate any significant changes to unrecognized tax benefits over the next twelve months. During the years ended December 31, 2015, 2014 and 2013, no significant interest or penalties were recognized relating to unrecognized tax benefits.

Segment Reporting

12 Months Ended

Dec. 31, 2015

Segment Reporting [Abstract]

Segment Reporting

Note 13 — Segment Reporting

We operate in one business segment which focuses on applying our technology platforms to improve the performance of established and novel medicines. We operate in one segment because our business offerings have similar economics and other characteristics, including the nature of products and manufacturing processes, types of customers, distribution methods and regulatory environment. We are comprehensively managed as one business segment by our Chief Executive Officer and his management team.

Our revenue is derived primarily from clients in the pharmaceutical and biotechnology industries. AstraZeneca and UCB represented 57% and 13% of our revenue, respectively, for the year ended December 31, 2015. Revenue from AstraZeneca, UCB and Roche represented 52%, 16% and 11% of our revenue, respectively, for the year ended December 31, 2014. Revenue from Roche, UCB, AstraZeneca and Bayer represented 28%, 21%, 17% and 10% of our revenue, respectively, for the year ended December 31, 2013.

Revenue by geographic area is based on the locations of our partners. The following table sets forth revenue by geographic area (in thousands):

	Year Ended December 31,
	2015		2014		2013
United States	$	40,400	$	32,514	$	42,535
Europe		190,384		168,193		106,386
Total revenue	$	230,784	$	200,707	$	148,921

At December 31, 2015, $54.2 million, or approximately 76%, of the net book value of our property, plant and equipment was located in the United States, $11.1 million, or approximately 16% was located at contract manufacturers in Germany and the Netherlands, and $6.0 million, or approximately 8%, was located in India. At December 31, 2014, $53.3 million, or approximately 76%, of the net book value of our property, plant and equipment was located in the United States, $10.4 million, or approximately 14% was located at contract manufacturers in Germany and the Netherlands, and $6.7 million, or approximately 10%, was located in India.

- Definition

The entire disclosure for reporting segments including data and tables. Reportable segments include those that meet any of the following quantitative thresholds a) it's reported revenue, including sales to external customers and intersegment sales or transfers is 10 percent or more of the combined revenue, internal and external, of all operating segments b) the absolute amount of its reported profit or loss is 10 percent or more of the greater, in absolute amount of 1) the combined reported profit of all operating segments that did not report a loss or 2) the combined reported loss of all operating segments that did report a loss c) its assets are 10 percent or more of the combined assets of all operating segments.

+ References

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Reference 3: http://www.xbrl.org/2003/role/presentationRef
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+ Details

Selected Quarterly Financial Data

12 Months Ended

Dec. 31, 2015

Quarterly Financial Information Disclosure [Abstract]

Selected Quarterly Financial Data

Note 14 — Selected Quarterly Financial Data (Unaudited)

The following table sets forth certain unaudited quarterly financial data. In our opinion, the unaudited information set forth below has been prepared on the same basis as our audited information and includes all adjustments necessary to present fairly the information set forth herein. We have experienced fluctuations in our quarterly results and expect these fluctuations to continue in the future. Due to these and other factors, we believe that quarter-to-quarter comparisons of our operating results will not be meaningful, and you should not rely on our results for any one quarter as an indication of our future performance. Certain items previously reported in specific financial statement captions have been reclassified to conform to the current period presentation. Such reclassifications have not materially impacted previously reported total revenues, operating loss or net loss. All data is in thousands except per share information.

	Fiscal Year Ended December 31, 2015											Fiscal Year Ended December 31, 2014
	Q1		Q2			Q3			Q4			Q1			Q2			Q3		Q4
Product sales	$	7,974	$	10,968		$	7,240		$	13,973		$	5,795		$	5,802		$	6,096	$	7,460
Total revenue	$	108,801	$	22,661		$	59,952		$	39,370		$	19,771		$	28,513		$	132,871	$	19,551
Cost of goods sold	$	8,444	$	10,534		$	6,760		$	8,364		$	7,907		$	5,108		$	9,220	$	6,298
Research and development expenses	$	47,011	$	45,412		$	43,229		$	47,135		$	38,338		$	36,702		$	34,200	$	38,494
Operating income (loss)	$	43,043	$	(43,469	)	$	419		$	(29,364	)	$	(36,402	)	$	(22,916	)	$	80,321	$	(37,488	)
Net income (loss)	$	33,820	$	(52,657	)	$	(8,203	)	$	(54,137	)	$	(46,201	)	$	(32,637	)	$	70,605	$	(45,683	)
Net income (loss) per share(1)
Basic	$	0.26	$	(0.40	)	$	(0.06	)	$	(0.40	)	$	(0.37	)	$	(0.26	)	$	0.55	$	(0.35	)
Diluted	$	0.25	$	(0.40	)	$	(0.06	)	$	(0.40	)	$	(0.37	)	$	(0.26	)	$	0.53	$	(0.35	)

(1)	Quarterly loss per share amounts may not total to the year-to-date loss per share due to rounding.

Organization and Summary of Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2015
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Organization	Organization We are a biopharmaceutical company headquartered in San Francisco, California and incorporated in Delaware. We are developing a pipeline of drug candidates that utilize our PEGylation and advanced polymer conjugate technology platforms with the objective to improve the benefits of drugs for patients. Our research and development activities have required significant ongoing investment to date and are expected to continue to require significant investment. As a result, we expect to continue to incur substantial losses and negative cash flows from operations in the future. We have financed our operations primarily through cash generated from licensing, collaboration and manufacturing agreements and financing transactions. At December 31, 2015, we had approximately $308.9 million in cash and investments in marketable securities. Also, as of December 31, 2015, we had $255.8 million in debt, including $250.0 million in principal of senior secured notes (as further discussed in Note 5) and $5.8 million of capital lease obligations (Note 6), of which $4.8 million is current.
Basis of Presentation, Principles of Consolidation and Use of Estimates	Basis of Presentation, Principles of Consolidation and Use of Estimates Our consolidated financial statements include the financial position, results of operations and cash flows of our wholly-owned subsidiaries: Nektar Therapeutics (India) Private Limited (Nektar India) and Nektar Therapeutics UK Limited. All intercompany accounts and transactions have been eliminated in consolidation. Our consolidated financial statements are denominated in U.S. dollars. Accordingly, changes in exchange rates between the applicable foreign currency and the U.S. dollar will affect the translation of each foreign subsidiary’s financial results into U.S. dollars for purposes of reporting our consolidated financial results. Translation gains and losses are included in accumulated other comprehensive income (loss) in the stockholders’ equity (deficit) section of the balance sheet. To date, such cumulative translation adjustments have not been significant to our consolidated financial position. Aggregate gross foreign currency transaction gains (losses) recorded in operations for the years ended December 31, 2015, 2014, and 2013 were not significant. The preparation of consolidated financial statements in conformity with U.S. generally accepted accounting principles (GAAP) requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the consolidated financial statements and the reported amounts of revenue and expenses during the reporting period. Accounting estimates and assumptions are inherently uncertain. Actual results could differ materially from those estimates and assumptions. Our estimates include those related to estimated selling prices of deliverables in collaboration agreements, estimated periods of performance, the net realizable value of inventory, the impairment of investments, the impairment of goodwill and long-lived assets, contingencies, accrued clinical trial expenses, estimated non-cash royalty revenue and interest expense from our liability related to our sale of future royalties, stock-based compensation, and ongoing litigation, among other estimates. We base our estimates on historical experience and on other assumptions that management believes are reasonable under the circumstances. These estimates form the basis for making judgments about the carrying values of assets and liabilities when these values are not readily apparent from other sources. As appropriate, estimates are assessed each period and updated to reflect current information and any changes in estimates will generally be reflected in the period identified.
Reclassifications	Reclassifications Certain items previously reported in specific financial statement captions have been reclassified to conform to the current period presentation. Such reclassifications do not materially impact previously reported revenue, operating loss, net loss, total assets, liabilities or stockholders’ equity.
Cash, Cash Equivalents, and Investments, and Fair Value of Financial Instruments	Cash, Cash Equivalents, and Investments, and Fair Value of Financial Instruments We consider all investments in marketable securities with an original maturity of three months or less when purchased to be cash equivalents. Investments in securities with remaining maturities of less than one year, or where our intent is to use the investments to fund current operations or to make them available for current operations, are classified as short-term investments. Investments are designated as available-for-sale and are carried at fair value, with unrealized gains and losses reported in stockholders’ equity (deficit) as accumulated other comprehensive income (loss). The disclosed fair value related to our cash equivalents and investments is based primarily on the reported fair values in our period-end brokerage statements, which are based on market prices from a variety of industry standard data providers and generally represent quoted prices for similar assets in active markets or have been derived from observable market data. We independently validate these fair values using available market quotes and other information. Interest and dividends on securities classified as available-for-sale, as well as amortization of premiums and accretion of discounts to maturity, are included in interest income. Realized gains and losses and declines in value of available-for-sale securities judged to be other-than-temporary, if any, are included in other income (expense). The cost of securities sold is based on the specific identification method. Our cash, cash equivalents, and short-term investments are exposed to credit risk in the event of default by the third parties that hold or issue such assets. Our cash, cash equivalents, and short-term investments are held by financial institutions that management believes are of high credit quality and our investment policy limits investments to fixed income securities denominated and payable in U.S. dollars such as U.S. government obligations, money market instruments and funds, and corporate bonds and places restrictions on maturities and concentrations by type and issuer.
Accounts Receivable and Significant Customer Concentrations	Accounts Receivable and Significant Customer Concentrations Our customers are primarily pharmaceutical and biotechnology companies that are located in the U.S. and Europe. Our accounts receivable balance contains billed and unbilled trade receivables from product sales, milestones, other contingent payments and royalties, as well as time and materials based billings from collaborative research and development agreements. When appropriate, we provide for an allowance for doubtful accounts by reserving for specifically identified doubtful accounts. We generally do not require collateral from our customers. We perform a regular review of our customers’ payment histories and associated credit risk. We have not experienced significant credit losses from our accounts receivable. At December 31, 2015, three different customers represented 50%, 35%, and 10%, respectively, of our accounts receivable. At December 31, 2014, three different customers represented 40%, 31%, and 15%, respectively, of our accounts receivable.
Inventory and Significant Supplier Concentrations	Inventory and Significant Supplier Concentrations Inventory is generally manufactured upon receipt of firm purchase orders from our collaboration partners. Inventory includes direct materials, direct labor, and manufacturing overhead and cost is determined on a first-in, first-out basis. Inventory is valued at the lower of cost or market and defective or excess inventory is written down to net realizable value based on historical experience or projected usage. Inventory related to our research and development activities is expensed when purchased. We are dependent on our suppliers and contract manufacturers to provide raw materials, drugs and devices of appropriate quality and reliability and to meet applicable contract and regulatory requirements. In certain cases, we rely on single sources of supply of one or more critical materials. Consequently, in the event that supplies are delayed or interrupted for any reason, our ability to develop and produce our drug candidates or our ability to meet our supply obligations could be significantly impaired, which could have a material adverse effect on our business, financial condition and results of operations.
Long-Lived Assets	Long-Lived Assets Property, plant and equipment are stated at cost. Major improvements are capitalized, while maintenance and repairs are expensed when incurred. Manufacturing, laboratory and other equipment are depreciated using the straight-line method generally over estimated useful lives of three to ten years. Leasehold improvements and buildings recorded under capital leases are depreciated using the straight-line method over the shorter of the estimated useful life or the remaining term of the lease. Goodwill represents the excess of the price paid for another entity over the fair value of the assets acquired and liabilities assumed in a business combination. We are organized in one reporting unit and evaluate the goodwill for the Company as a whole. Goodwill has an indefinite useful life and is not amortized, but instead tested for impairment at least annually in the fourth quarter of each year using an October 1 measurement date. We assess the impairment of long-lived assets, primarily property, plant and equipment and goodwill, whenever events or changes in business circumstances indicate that the carrying amounts of the assets may not be fully recoverable. When such events occur, we determine whether there has been an impairment in value by comparing the carrying value of the asset with its fair value, as measured by the anticipated undiscounted net cash flows of the asset. In the case of goodwill impairment, market capitalization is generally used as the measure of fair value. If an impairment in value exists, the asset is written down to its estimated fair value. In March 2015, we announced that the primary endpoint for our BEACON Phase 3 clinical study for NKTR-102 as a single-agent therapy for women with advanced metastatic breast cancer did not achieve statistical significance. As a result, we performed an impairment analysis for our long-lived assets, including goodwill, as well as our primary long-lived asset group which is related to NKTR-102. Based on this analysis, we concluded that there is no impairment during the year ended December 31, 2015.
Revenue Recognition	Revenue Recognition Our revenue is derived from our arrangements with pharmaceutical and biotechnology collaboration partners and may result from one or more of the following: upfront and license fees, payments for contract research and development, milestone and other contingent payments, manufacturing and supply payments, and royalties. Our performance obligations under our collaborations may include licensing our intellectual property, manufacturing and supply obligations, and research and development obligations. In order to account for the multiple-element arrangements, we identify the deliverables included within the arrangement and evaluate which deliverables represent separate units of accounting. Analyzing the arrangement to identify deliverables requires the use of judgment, and each deliverable may be an obligation to deliver goods or services, a right or license to use an asset, or another performance obligation. Revenue is recognized separately for each identified unit of accounting when the basic revenue recognition criteria are met: there is persuasive evidence that an arrangement exists, delivery has occurred, the price is fixed or determinable, and collection is reasonably assured. At the inception of each new multiple-element arrangement or the material modification of an existing multiple-element arrangement, we allocate all consideration received under multiple-element arrangements to all units of accounting based on the relative selling price method, generally based on our best estimate of selling price (ESP). The objective of ESP is to determine the price at which we would transact a sale if the product or service was sold on a stand-alone basis. We determine ESP for the elements in our collaboration arrangements by considering multiple factors including, but not limited to, technical complexity of the performance obligation and similarity of elements to those performed under previous arrangements. Since we apply significant judgment in arriving at the ESPs, any material change in our estimates would significantly affect the allocation of the total consideration to the different elements of a multiple element arrangement. Product sales Product sales are primarily derived from fixed price and cost-plus manufacturing and supply agreements with our collaboration partners. We have not experienced any significant returns from our customers. Royalty revenue Generally, we are entitled to royalties from our collaboration partners based on the net sales of their approved drugs that are marketed and sold in one or more countries where we hold royalty rights. We recognize royalty revenue when the cash is received or when the royalty amount to be received is estimable and collection is reasonably assured. With respect to the non-cash royalties related to sale of future royalties described in Note 7, revenue is recognized when estimable, otherwise, revenue is recognized during the period in which the related royalty report is received, which generally occurs in the quarter after the applicable product sales are made. License, collaboration and other revenue The amount of upfront fees and other payments received by us in license and collaboration arrangements that are allocated to continuing performance obligations, such as manufacturing and supply obligations, are deferred and generally recognized ratably over our expected performance period under each respective arrangement. We make our best estimate of the period over which we expect to fulfill our performance obligations, which may include technology transfer assistance, research activities, clinical development activities, and manufacturing activities from development through the commercialization of the product. Given the uncertainties of these collaboration arrangements, significant judgment is required to determine the duration of the performance period and this estimate is periodically re-evaluated. Contingent consideration received from the achievement of a substantive milestone is recognized in its entirety in the period in which the milestone is achieved, which we believe is consistent with the substance of our performance under our various license and collaboration agreements. A milestone is defined as an event (i) that can only be achieved based in whole or in part either on the entity’s performance or on the occurrence of a specific outcome resulting from the entity’s performance, (ii) for which there is substantive uncertainty at the date the arrangement is entered into that the event will be achieved, and (iii) that would result in additional payments being due to the entity. A milestone is substantive if the consideration earned from the achievement of the milestone is consistent with our performance required to achieve the milestone or the increase in value to the collaboration resulting from our performance, relates solely to our past performance, and is reasonable relative to all of the other deliverables and payments within the arrangement. Our license and collaboration agreements with our partners provide for payments to us upon the achievement of development milestones, such as the completion of clinical trials or regulatory submissions, approvals by regulatory authorities, and commercial launches of drugs. Given the challenges inherent in developing and obtaining regulatory approval for drug products and in achieving commercial launches, there was substantial uncertainty whether any such milestones would be achieved at the time of execution of these licensing and collaboration agreements. In addition, we evaluated whether the development milestones met the remaining criteria to be considered substantive. As a result of our analysis, we consider our remaining development milestones under all of our license and collaboration agreements to be substantive and, accordingly, we expect to recognize as revenue future payments received from each milestone only if and as such milestone is achieved. Our license and collaboration agreements with certain partners also provide for contingent payments to us based solely upon the performance of the respective partner. For such contingent amounts, we expect to recognize the payments as revenue when earned under the applicable contract, which is generally upon completion of performance by the respective partner, provided that collection is reasonably assured. Our license and collaboration agreements with our partners also provide for payments to us upon the achievement of specified sales volumes of approved drugs. We consider these payments to be similar to royalty payments and we will recognize such sales-based payments upon achievement of such sales volumes, provided that collection is reasonably assured.
Shipping and Handling Costs	Shipping and Handling Costs We recognize costs related to shipping and handling of product to customers in cost of goods sold.
Research and Development Expense	Research and Development Expense Research and development costs are expensed as incurred and include salaries, benefits and other operating costs such as outside services, supplies and allocated overhead costs. We perform research and development for our proprietary drug candidates and technology development and for certain third parties under collaboration agreements. For our proprietary drug candidates and our internal technology development programs, we invest our own funds without reimbursement from a third party. We record accruals for the estimated costs of our clinical trial activities performed by third parties. The financial terms of these agreements are subject to negotiation, vary from contract to contract and may result in uneven payment flows to our vendors. Payments under the contracts depend on factors such as the achievement of certain events, successful enrollment of patients, and completion of certain clinical trial activities. We generally accrue costs associated with the start-up and reporting phases of the clinical trials ratably over the estimated duration of the start-up and reporting phases. We generally accrue costs associated with the treatment phase of clinical trials based on the total estimated cost of the treatment phase on a per patient basis and we expense the per patient cost ratably over the estimated patient treatment period based on patient enrollment in the trials. In specific circumstances, such as for certain time-based costs, we recognize clinical trial expenses using a methodology that we consider to be more reflective of the timing of costs incurred. Advance payments for goods or services that will be used or rendered for future research and development activities are capitalized as prepaid expenses and recognized as expense as the related goods are delivered or the related services are performed. We base our estimates on the best information available at the time. However, additional information may become available to us which may allow us to make a more accurate estimate in future periods. In this event, we may be required to record adjustments to research and development expenses in future periods when the actual level of activity becomes more certain. Such increases or decreases in cost are generally considered to be changes in estimates and will be reflected in research and development expenses in the period identified. .
Stock-Based Compensation	Stock-Based Compensation Stock-based compensation arrangements include stock option grants and restricted stock unit (RSU) awards under our equity incentive plans, as well as shares issued under our Employee Stock Purchase Plan (ESPP), through which employees may purchase our common stock at a discount to the market price. We use the Black-Scholes option pricing model for the respective grant to determine the estimated fair value of the option on the date of grant (grant date fair value) and the estimated fair value of common stock purchased under the ESPP. The Black-Scholes option pricing model requires the input of highly subjective assumptions. These variables include, but are not limited to, our stock price volatility over the term of the awards, and actual and projected employee stock option exercise behaviors. Because our employee stock options have characteristics significantly different from those of traded options, and because changes in the subjective input assumptions can materially affect the fair value estimate, in management’s opinion, the existing models may not provide a reliable single measure of the fair value of our employee stock options or common stock purchased under the ESPP. Management will continue to assess the assumptions and methodologies used to calculate the estimated fair value of stock-based compensation. Circumstances may change and additional data may become available over time, which could result in changes to these assumptions and methodologies, and which could materially impact our fair value determination. We expense the value of the portion of the option or award that is ultimately expected to vest based on the historical forfeiture rate on a straight line basis over the requisite service periods in our Consolidated Statements of Operations. For awards that vest upon the achievement of performance milestones, we estimate the vesting period based on our evaluation of the probability of achievement of each respective milestone and the related estimated date of achievement. Stock-based compensation expense for purchases under the ESPP is recognized over the respective six-month purchase period. Expense amounts are recorded in cost of goods sold, research and development expense, and general and administrative expense based on the function of the applicable employee. Stock-based compensation charges are non-cash charges and as such have no impact on our reported cash flows.
Net Loss Per Share	Net Loss Per Share Basic net loss per share is calculated based on the weighted-average number of common shares outstanding during the periods presented. For all periods presented in the Consolidated Statements of Operations, the net loss available to common stockholders is equal to the reported net loss. Basic and diluted net loss per share are the same due to our historical net losses and the requirement to exclude potentially dilutive securities which would have an anti-dilutive effect on net loss per share. During 2015, 2014 and 2013, potentially dilutive securities consisted of common shares underlying outstanding stock options and restricted stock unit awards (RSUs). There were weighted average outstanding stock options and RSUs of 21.1 million, 21.9 million and 20.7 million during the years ended December 31, 2015, 2014 and 2013, respectively.
Income Taxes	Income Taxes We account for income taxes under the liability method. Under this method, deferred tax assets and liabilities are determined based on differences between the financial reporting and tax reporting bases of assets and liabilities and are measured using enacted tax rates and laws that are expected to be in effect when the differences are expected to reverse. Realization of deferred tax assets is dependent upon future earnings, the timing and amount of which are uncertain. We record a valuation allowance against deferred tax assets to reduce their carrying value to an amount that is more likely than not to be realized. When we establish or reduce the valuation allowance related to the deferred tax assets, our provision for income taxes will increase or decrease, respectively, in the period such determination is made. We utilize a two-step approach to recognize and measure uncertain tax positions. The first step is to evaluate the tax position for recognition by determining if the weight of available evidence indicates that it is more likely than not that the position will be sustained upon tax authority examination, including resolution of related appeals or litigation processes, if any. The second step is to measure the tax benefit as the largest amount that is more than 50% likely of being realized upon ultimate settlement.
Comprehensive loss	Comprehensive loss Comprehensive loss is the change in stockholders’ equity (deficit) from transactions and other events and circumstances other than those resulting from investments by stockholders and distributions to stockholders. Our other comprehensive income (loss) is comprised of net loss, gains and losses from the foreign currency translation of the assets and liabilities of our India and UK subsidiaries, and unrealized gains and losses on investments in available-for-sale securities.
Recent Accounting Pronouncements	Recent Accounting Pronouncements In May 2014, the Financial Accounting Standards Board (FASB) issued guidance codified in Accounting Standards Codification (ASC) 606, Revenue Recognition — Revenue from Contracts with Customers, which amends the guidance in former ASC 605, Revenue Recognition, and is effective for public companies for fiscal years beginning after December 15, 2017. Entities have the option of using either a full retrospective or a modified retrospective approach to adopt this new guidance. We are currently evaluating the impact of the provisions of ASC 606. In April 2015, the FASB issued guidance to simplify the presentation of debt issuance costs by requiring debt issuance costs to be presented as a deduction from the corresponding debt liability. This guidance is effective for our interim and annual periods beginning January 1, 2016 and early adoption is permitted. Upon adoption, the new guidance must be applied retrospectively to all periods presented. We do not believe the adoption of this guidance will have a material impact on our consolidated financial statements.
Royalty Monetization Interest	As royalties are remitted to RPI from Roche and UCB, the balance of the Royalty Obligation will be effectively repaid over the life of the agreement. In order to determine the amortization of the Royalty Obligation, we are required to estimate the total amount of future royalty payments to be received by RPI and payments we are required to make to RPI as noted above over the life of the agreement. The sum of these amounts less the $124.0 million proceeds we received will be recorded as interest expense over the life of the Royalty Obligation. Since inception, our estimate of this total interest expense resulted in an effective annual interest rate of approximately 17%. We periodically assess the estimated royalty payments to RPI from UCB and Roche and to the extent the amount or timing of such payments is materially different than our original estimates, we will prospectively adjust the amortization of the Royalty Obligation. There are a number of factors that could materially affect the amount and timing of royalty payments from CIMZIA^® and MIRCERA^®, most of which are not within our control. Such factors include, but are not limited to, changing standards of care, the introduction of competing products, manufacturing or other delays, biosimilar competition, intellectual property matters, adverse events that result in governmental health authority imposed restrictions on the use of the drug products, significant changes in foreign exchange rates as the royalties remitted to RPI are made in U.S. dollars (USD) while significant portions of the underlying sales of CIMZIA^® and MIRCERA^® are made in currencies other than USD, and other events or circumstances that could result in reduced royalty payments from CIMZIA^® and MIRCERA^®, all of which would result in a reduction of non-cash royalty revenues and the non-cash interest expense over the life of the Royalty Obligation. Conversely, if sales of CIMZIA^® and MIRCERA^® are more than expected, the non-cash royalty revenues and the non-cash interest expense recorded by us would be greater over the term of the Royalty Obligation.

Cash and Investments in Marketable Securities (Tables)

12 Months Ended

Dec. 31, 2015

Fair Value Disclosures [Abstract]

Cash and Investments in Marketable Securities, Including Cash Equivalents and Restricted Cash

Cash and investments in marketable securities, including cash equivalents and restricted cash, are as follows (in thousands).

	Estimated Fair Value at
	December 31, 2015		December 31, 2014
Cash and cash equivalents	$	55,570	$	12,365
Short-term investments		253,374		225,459
Restricted cash		—		25,000
Total cash and investments in marketable securities	$	308,944	$	262,824

Portfolio of Cash and Investments in Marketable Securities

Our portfolio of cash and investments in marketable securities includes (in thousands):

			Estimated Fair Value at
	Fair Value Hierarchy Level		December 31, 2015		December 31, 2014
Corporate notes and bonds		2	$	181,969	$	182,544
Corporate commercial paper		2		61,150		42,915
Obligations of U.S. government agencies		2		7,325		—
Available-for-sale investments				250,444		225,459
Money market funds		1		53,728		11,229
Certificate of deposit	N/A			2,930		—
Cash, including restricted cash	N/A			1,842		26,136
Total cash and investments in marketable securities			$	308,944	$	262,824

Inventory (Tables)

12 Months Ended

Dec. 31, 2015

Inventory Disclosure [Abstract]

Inventory

Inventory consists of the following (in thousands):

	December 31,
	2015		2014
Raw materials	$	3,236	$	2,200
Work-in-process		6,087		5,187
Finished goods		2,023		5,565
Total inventory	$	11,346	$	12,952

Property, Plant and Equipment (Tables)

12 Months Ended

Dec. 31, 2015

Property Plant And Equipment [Abstract]

Property, Plant and Equipment

Property, plant and equipment consists of the following (in thousands):

	December 31,
	2015			2014
Building and leasehold improvements	$	77,665		$	72,228
Laboratory equipment		27,309			26,975
Manufacturing equipment		35,631			25,212
Furniture, fixtures and other equipment		24,987			23,451
Depreciable property, plant and equipment at cost		165,592			147,866
Less: accumulated depreciation		(102,712	)		(93,807	)
Depreciable property, plant and equipment, net		62,880			54,059
Construction-in-progress		8,456			16,309
Property, plant and equipment, net	$	71,336		$	70,368

Leases (Tables)

12 Months Ended

Dec. 31, 2015

Leases [Abstract]

Future Minimum Payments for Capital Leases

Future minimum payments for our capital leases at December 31, 2015 are as follows (in thousands):

Years ending December 31,
2016	$	5,135
2017		1,043
2018		72
Total minimum payments required		6,250
Less: amount representing interest		(421	)
Present value of future minimum lease payments		5,829
Less: current portion		(4,756	)
Capital lease obligation, less current portion	$	1,073

Future Minimum Lease Payments for Operating Leases

Our future minimum lease payments for our operating leases at December 31, 2015 are as follows (in thousands):

Years ending December 31,
2016	$	4,892
2017		5,037
2018		5,187
2019		5,344
2020		452
Total future minimum lease payments	$	20,912

Liability Related to the Sale of Future Royalties (Tables)

12 Months Ended

Dec. 31, 2015

Summary of Liability Related to Potential Future Royalties

	Year ended December 31, 2015			Period from inception to December 31, 2015
Liability related to the sale of future royalties—beginning balance	$	120,471		$	—
Proceeds from sale of future royalties		—			124,000
Payments from Nektar to RPI		—			(10,000	)
Non-cash CIMZIA^® and MIRCERA^® royalty revenue		(22,058	)		(76,841	)
Non-cash interest expense recognized		20,619			81,873
Liability related to the sale of future royalties – ending balance	$	119,032		$	119,032

Stockholders' Equity (Tables)

12 Months Ended

Dec. 31, 2015

Equity [Abstract]

Summarization of Common Stock Shares for Issuance Under Existing Equity Compensation Plans

Plan Category	Number of Securities to be Issued Upon Exercise of Outstanding Options & Vesting of RSUs (a)		Weighted- Average Exercise Price of Outstanding Options (b)		Number of Securities Remaining Available for Issuance Under Equity Compensation Plans (Excluding Securities Reflected in Column(a) (c)
Equity compensation plans approved by security holders(1)		18,056	$	11.33		7,657
Equity compensation plans not approved by security holders		2,032	$	10.30		—
Total		20,088	$	11.22		7,657

(1)	Includes shares of common stock available for future issuance under our ESPP as of December 31, 2015.

License and Collaboration Agreements (Tables)

12 Months Ended

Dec. 31, 2015

Organization Consolidation And Presentation Of Financial Statements [Abstract]

License, Collaboration and Other Revenue

In accordance with our collaboration agreements, we recognized license, collaboration and other revenue as follows (in thousands):

		Year Ended December 31,
Partner	Agreement	2015		2014		2013
AstraZeneca AB	MOVANTIK^TM (NKTR-118) and MOVANTIK^TM fixed-dose combination program (NKTR-119)	$	130,000	$	105,001	$	25,016
Roche	PEGASYS^® and MIRCERA^®		12,816		12,845		18,382
Baxalta Incorporated	ADYNOVATE^TM		10,694		10,258		1,702
Amgen, Inc.	Neulasta^®		5,000		5,000		5,035
Bayer Healthcare LLC	BAY41-6551 (Amikacin Inhale)		1,919		4,717		15,293
Affymax, Inc.	OMONTYS^®		—		—		7,149
Other			5,175		15,468		8,295
License, collaboration and other revenue		$	165,604	$	153,289	$	80,872

Stock-Based Compensation (Tables)

12 Months Ended

Dec. 31, 2015

Stock-Based Compensation Expense

We issue stock-based awards from our equity incentive plans, which are more fully described in Note 9. Stock-based compensation expense was recognized as follows (in thousands):

	Year Ended December 31,
	2015		2014		2013
Cost of goods sold	$	1,142	$	1,161	$	1,297
Research and development		9,207		7,528		7,910
General and administrative		9,320		8,328		8,501
Total stock-based compensation	$	19,669	$	17,017	$	17,708

Black-Scholes Option-Pricing Model Assumptions Used to Calculate Fair Value of Employee Stock Options

The following table lists the Black-Scholes option-pricing model assumptions used to calculate the fair value of employee and director stock options.

	Year Ended December 31,
	2015			2014			2013
Average risk-free interest rate		1.6	%		1.6	%		0.9	%
Dividend yield		0.0	%		0.0	%		0.0	%
Average volatility factor		50.8	%		51.6	%		61.2	%
Average weighted average expected life	5.3 years			5.2 years			5.2 years

Stock Option Activity Under Equity Incentive Plans

The table below presents a summary of stock option activity under our equity incentive plans (in thousands, except for price per share and contractual life information):

	Number of Shares			Weighted- Average Exercise Price per Share		Weighted- Average Remaining Contractual Life (in Years)		Aggregate Intrinsic Value(1)
Outstanding at December 31, 2014		21,995		$	10.50
Options granted		1,746			14.00
Options exercised		(3,937	)		7.89
Options forfeited & canceled		(1,022	)		13.42
Outstanding at December 31, 2015		18,782		$	11.22		4.67	$	105,830

Vested and expected to vest at December 31, 2015		18,360		$	11.14		4.62	$	104,749
Exercisable at December 31, 2015		12,222		$	9.89		3.60	$	85,074

(1)	Aggregate intrinsic value represents the difference between the exercise price of the option and the closing market price of our common stock on December 31, 2015.

Restricted Stock Units (RSU) [Member]

Restricted Stock Unit Award Activity

A summary of RSU award activity is as follows (in thousands except for per share amounts):

	Units Issued		Weighted- Average Grant Date Fair Value		Aggregate Intrinsic Value(1)
Balance at December 31, 2014		—
Granted		1,306	$	15.30
Vested		—
Forfeited and canceled		—
Balance at December 31, 2015		1,306			$	22,012

(1)	Aggregate intrinsic value represents the difference between the grant price of the award and the closing market price of our common stock on December 31, 2015.

Income Taxes (Tables)

12 Months Ended

Dec. 31, 2015

Income Tax Disclosure [Abstract]

Loss Before Provision (Benefit) for Income Taxes

Loss before provision (benefit) for income taxes includes the following components (in thousands):

	Year Ended December 31,
	2015			2014			2013
Domestic	$	(81,931	)	$	(56,414	)	$	(161,068	)
Foreign		1,260			1,986			1,300
Loss before provision (benefit) for income taxes	$	(80,671	)	$	(54,428	)	$	(159,768	)

Provision (Benefit) for Income Taxes

The provision (benefit) for income taxes consists of the following (in thousands):

	Year Ended December 31,
	2015			2014			2013
Current:
Federal	$	—		$	—		$	—
State		(1	)		1			1
Foreign		529			(482	)		1,838
Total Current		528			(481	)		1,839
Deferred:
Federal		—			—			422
State		—			—			49
Foreign		(22	)		(31	)		(65	)
Total Deferred		(22	)		(31	)		406
Provision (benefit) for income taxes	$	506		$	(512	)	$	2,245

Income Tax Provision Related to Continuing Operations

Income tax provision related to continuing operations differs from the amount computed by applying the statutory income tax rate of 35% to pretax loss as follows (in thousands):

	Year Ended December 31,
	2015			2014			2013
U.S. federal provision (benefit)
At statutory rate	$	(28,235	)	$	(19,050	)	$	(55,919	)
State taxes		(1	)		1			50
Change in valuation allowance		22,210			11,831			55,042
Non-cash interest expense on liability related to sale of future royalties		7,217			7,311			7,808
Stock-based compensation		674			2,832			271
Foreign tax inclusion		1,773			—			—
Foreign tax differential		(7	)		(17	)		(20	)
Research credits		(4,529	)		(2,933	)		(6,273	)
Other		1,404			(487	)		1,286
Provision (benefit) for income taxes	$	506		$	(512	)	$	2,245

Significant Components of Deferred Tax Assets and Liabilities

Significant components of our deferred tax assets for federal and state income taxes are as follows (in thousands):

	December 31,
	2015			2014
Deferred tax assets:
Net operating loss carryforwards	$	447,761		$	423,776
Research and other credits		70,258			66,666
Deferred revenue		29,658			29,758
Stock-based compensation		22,832			21,948
Capitalized research expenses		12,440			14,795
Sale of future royalties		12,319			20,153
Reserves and accruals		8,309			8,288
Property, plant and equipment		6,451			8,264
Other		3,158			2,218
Deferred tax assets before valuation allowance		613,186			595,866
Valuation allowance for deferred tax assets		(612,996	)		(595,690	)
Total deferred tax assets		190			176
Total deferred tax liabilities		—			—
Net deferred tax assets	$	190		$	176

Unrecognized Tax Benefits

We have the following activity relating to unrecognized tax benefits (in thousands):

	December 31,
	2015			2014			2013
Beginning balance	$	27,522		$	16,363		$	14,067
Tax positions related to current year
Additions:
Federal		529			502			477
State		443			6,141			381
Reductions		—			—			—
Tax positions related to prior year
Additions:
Federal		—			—			636
State		—			5,258			—
Foreign		—			—			802
Reductions		(11,110	)		(742	)		—
Settlements		—			—			—
Lapses in statute of limitations		—			—			—
Ending balance	$	17,384		$	27,522		$	16,363

Segment Reporting (Tables)

12 Months Ended

Dec. 31, 2015

Segment Reporting [Abstract]

Revenue by Geographic Area

Revenue by geographic area is based on the locations of our partners. The following table sets forth revenue by geographic area (in thousands):

	Year Ended December 31,
	2015		2014		2013
United States	$	40,400	$	32,514	$	42,535
Europe		190,384		168,193		106,386
Total revenue	$	230,784	$	200,707	$	148,921

Selected Quarterly Financial Data (Tables)

12 Months Ended

Dec. 31, 2015

Quarterly Financial Information Disclosure [Abstract]

Quarterly Financial Data

	Fiscal Year Ended December 31, 2015											Fiscal Year Ended December 31, 2014
	Q1		Q2			Q3			Q4			Q1			Q2			Q3		Q4
Product sales	$	7,974	$	10,968		$	7,240		$	13,973		$	5,795		$	5,802		$	6,096	$	7,460
Total revenue	$	108,801	$	22,661		$	59,952		$	39,370		$	19,771		$	28,513		$	132,871	$	19,551
Cost of goods sold	$	8,444	$	10,534		$	6,760		$	8,364		$	7,907		$	5,108		$	9,220	$	6,298
Research and development expenses	$	47,011	$	45,412		$	43,229		$	47,135		$	38,338		$	36,702		$	34,200	$	38,494
Operating income (loss)	$	43,043	$	(43,469	)	$	419		$	(29,364	)	$	(36,402	)	$	(22,916	)	$	80,321	$	(37,488	)
Net income (loss)	$	33,820	$	(52,657	)	$	(8,203	)	$	(54,137	)	$	(46,201	)	$	(32,637	)	$	70,605	$	(45,683	)
Net income (loss) per share(1)
Basic	$	0.26	$	(0.40	)	$	(0.06	)	$	(0.40	)	$	(0.37	)	$	(0.26	)	$	0.55	$	(0.35	)
Diluted	$	0.25	$	(0.40	)	$	(0.06	)	$	(0.40	)	$	(0.37	)	$	(0.26	)	$	0.53	$	(0.35	)

(1)	Quarterly loss per share amounts may not total to the year-to-date loss per share due to rounding.

Organization and Summary of Significant Accounting Policies - Additional Information (Detail) shares in Millions	12 Months Ended
	Dec. 31, 2015 USD ($) Customer Reporting_Unit shares	Dec. 31, 2014 USD ($) Customer shares	Dec. 31, 2013 shares
Organization And Summary Of Significant Accounting Policies [Line Items]
Cash and investments in marketable securities	$ 308,944,000	$ 262,824,000
Senior secured notes	250,000,000
Debt and capital lease obligation	255,800,000
Capital lease obligations	5,800,000
Capital lease obligations, current portion	$ 4,756,000	$ 4,512,000
Number of customers accounted for major accounts receivable \| Customer	3	3
Percentage of accounts receivable customers one	50.00%	40.00%
Percentage of accounts receivable customers two	35.00%	31.00%
Percentage of accounts receivable customers three	10.00%	15.00%
Number of reporting unit evaluated for goodwill \| Reporting_Unit	1
Asset impairment charges	$ 0
Minimum percentage of amount realized upon ultimate settlement	50.00%
Stock Options and Restricted Stock Units [Member]
Organization And Summary Of Significant Accounting Policies [Line Items]
Weighted average diluted securities excluded from diluted net loss per share \| shares	21.1	21.9	20.7
Minimum [Member]
Organization And Summary Of Significant Accounting Policies [Line Items]
Property and equipment estimated useful lives	3 years
Maximum [Member]
Organization And Summary Of Significant Accounting Policies [Line Items]
Property and equipment estimated useful lives	10 years

Cash and Investments in Marketable Securities - Cash and Investments in Marketable Securities, Including Cash Equivalents and Restricted Cash (Detail) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Cash and cash equivalents	$ 55,570	$ 12,365	$ 39,067	$ 25,437
Short-term investments	253,374	225,459
Restricted cash	0	25,000
Total cash and investments in marketable securities	$ 308,944	$ 262,824

Cash and Investments in Marketable Securities - Additional Information (Detail) - USD ($)		12 Months Ended
	Oct. 05, 2015	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Cash and Investments in Marketable Securities [Line Items]
Maximum maturity term for debt securities investment		Two years or less
Weighted average maturity term for debt securities investment		One year or less
Available-for-sale securities, sold		$ 42,500,000	$ 21,700,000	$ 2,900,000
Restricted cash		0	25,000,000
Level 1 to level 2 transfers		0	0	0
Level 2 to level 1 transfers		0	0	$ 0
Letter of credit		$ 2,400,000	$ 2,400,000
7.75% Senior Secured Notes Due October 2020 [Member]
Cash and Investments in Marketable Securities [Line Items]
Senior secured notes, interest rate		7.75%
Senior Notes [Member] \| 12% Senior Secured Notes Due July 2017 [Member]
Cash and Investments in Marketable Securities [Line Items]
Restricted cash	$ 25,000,000
Senior secured notes, interest rate	12.00%
Senior secured notes, maturity date	Jul. 15, 2017
Senior Notes [Member] \| 7.75% Senior Secured Notes Due October 2020 [Member]
Cash and Investments in Marketable Securities [Line Items]
Senior secured notes, interest rate	7.75%	7.75%
Senior secured notes, maturity date		Oct. 05, 2020
Minimum cash and investments in marketable securities to be maintained		$ 60,000,000

Cash and Investments in Marketable Securities - Portfolio of Cash and Investments in Marketable Securities (Detail) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale investments	$ 250,444	$ 225,459
Cash, including restricted cash	1,842	26,136
Total cash and investments in marketable securities	308,944	262,824
Corporate Notes and Bonds [Member] \| Fair Value Hierarchy Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale investments	181,969	182,544
Corporate Commercial Paper [Member] \| Fair Value Hierarchy Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale investments	61,150	42,915
Obligations of U.S. government agencies [Member] \| Fair Value Hierarchy Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale investments	7,325	0
Money Market Funds [Member] \| Fair Value Hierarchy Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments in marketable securities	53,728	11,229
Certificates of Deposit [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments in marketable securities	$ 2,930	$ 0

Inventory - Inventory (Detail) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Inventory Disclosure [Abstract]
Raw materials	$ 3,236	$ 2,200
Work-in-process	6,087	5,187
Finished goods	2,023	5,565
Total inventory	$ 11,346	$ 12,952

Property, Plant and Equipment - Property, Plant and Equipment (Detail) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Property, Plant and Equipment [Line Items]
Depreciable property and equipment at cost	$ 165,592	$ 147,866
Less: accumulated depreciation	(102,712)	(93,807)
Depreciable property, plant and equipment, net	62,880	54,059
Construction-in-progress	8,456	16,309
Property plant and equipment, net	71,336	70,368
Building and Leasehold Improvements [Member]
Property, Plant and Equipment [Line Items]
Depreciable property and equipment at cost	77,665	72,228
Laboratory Equipment [Member]
Property, Plant and Equipment [Line Items]
Depreciable property and equipment at cost	27,309	26,975
Manufacturing Equipment [Member]
Property, Plant and Equipment [Line Items]
Depreciable property and equipment at cost	35,631	25,212
Furniture, Fixtures and Other Equipment [Member]
Property, Plant and Equipment [Line Items]
Depreciable property and equipment at cost	$ 24,987	$ 23,451

Property, Plant and Equipment - Additional Information (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Property Plant And Equipment [Abstract]
Obligation related to purchase of equipment	$ 4.3	$ 7.2
Obligation related to purchase of equipment liability payable term	3 years
Depreciation expense	$ 11.4	$ 11.7	$ 13.0

Senior Secured Notes - Additional Information (Detail) - USD ($)		1 Months Ended	12 Months Ended
	Oct. 05, 2015	Nov. 30, 2015	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Line of Credit Facility [Line Items]
Cash paid for interest			$ 20,225,000	$ 17,445,000	$ 17,590,000
Loss on extinguishment of debt			14,079,000	0	0
Write-off of unamortized issuance costs			$ 1,579,000	$ 0	$ 0
Percentage of repurchase of notes on principal amount of notes			101.00%
Percentage of repurchase of notes on principal amount of notes upon sale of assets			100.00%
Senior Secured Notes principal amount			$ 250,000,000
7.75% Senior Secured Notes Due October 2020 [Member]
Line of Credit Facility [Line Items]
Senior secured notes, interest rate			7.75%
Senior Notes [Member] \| 7.75% Senior Secured Notes Due October 2020 [Member]
Line of Credit Facility [Line Items]
Senior secured notes, issued	$ 250,000,000
Senior secured notes, interest rate	7.75%		7.75%
Senior secured notes, maturity date			Oct. 05, 2020
Frequency of payment			Quarterly
Date of first repayment			Oct. 15, 2015
Issuance costs	$ 8,900,000
Debt discount on transaction and facility fees	8,300,000
Direct debt issuance costs capitalized	400,000
Additional issuance costs	200,000
Debt instrument term			5 years
Senior secured notes, cash received	$ 100,300,000
Minimum cash and investments in marketable securities to be maintained			$ 60,000,000
Restricted cash to be maintained until release of 12% Notes liens		$ 50,000,000
Senior Notes [Member] \| 12% Senior Secured Notes Due July 2017 [Member]
Line of Credit Facility [Line Items]
Senior secured notes, interest rate	12.00%
Senior secured notes, maturity date	Jul. 15, 2017
Repayment of senior secured notes	$ 125,000,000
Accrued interest paid on 12% notes at redemption	3,300,000
Redemption premium	12,500,000		11,300,000
Cash paid for interest	1,200,000		1,200,000
Loss on extinguishment of debt			$ 14,100,000
Write-off of unamortized issuance costs	$ 1,600,000

Leases - Additional Information (Detail) $ in Millions	12 Months Ended
Leases - Additional Information (Detail) $ in Millions	Dec. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)	Dec. 31, 2013 USD ($)	Sep. 30, 2009 ft²
Leases [Line Items]
Percentage ceiling on rent increases, annually, capital lease	3.00%
San Carlos facility capital leases, termination date	Oct. 05, 2016
Future minimum rental receipts under the San Carlos facility subleases	$ 2.1
Book value of assets, gross	5.1	$ 2.7
Net book value of assets	$ 3.2	1.2
Operating Sublease term commenced start date	2010-08
Operating Sublease term commenced period	114 months
Operating Sublease term commenced end date	January 31, 2020
Rent expense for operating leases	$ 3.2	3.2	$ 2.9
Deferred rent	$ 8.5	$ 8.7
Pfizer, Inc. [Member]
Leases [Line Items]
Operating sublease \| ft²				126,285

Leases - Future Minimum Payments for Capital Leases (Detail) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Leases [Abstract]
2016	$ 5,135
2017	1,043
2018	72
Total minimum payments required	6,250
Less: amount representing interest	(421)
Present value of future minimum lease payments	5,829
Less: current portion	(4,756)	$ (4,512)
Capital lease obligation, less current portion	$ 1,073	$ 4,139

Leases - Future Minimum Lease Payments for Operating Leases (Detail) $ in Thousands	Dec. 31, 2015 USD ($)
Leases [Abstract]
2016	$ 4,892
2017	5,037
2018	5,187
2019	5,344
2020	452
Total future minimum lease payments	$ 20,912

Liability Related to the Sale of Future Royalties - Additional Information (Detail) - USD ($) $ in Thousands		1 Months Ended		12 Months Ended			46 Months Ended
	Feb. 24, 2012	Mar. 31, 2014	Mar. 31, 2013	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2015
Liability Related to the Sale of Future Royalties [Line Items]
Royalty agreement contingent payment description				As a result of worldwide net sales of MIRCERA® for the 12 month periods ended December 31, 2013 and 2012 not reaching certain minimum thresholds.
Non-cash royalty revenue related to sale of future royalties				$ 22,058	$ 21,937	$ 22,055	$ 76,841
Non-cash interest expense on liability related to sale of future royalties				$ 20,619	$ 20,888	$ 22,309	$ 81,873
Annual interest rate				17.00%
Purchase and Sale Agreement with RPI [Member]
Liability Related to the Sale of Future Royalties [Line Items]
Proceeds from sale of royalty rights	$ 124,000
Transaction costs related to sale of potential future royalties	$ 4,400
Payment made for milestone not achieved year two		$ 7,000
Payment made for milestone not achieved year one			$ 3,000

Liability Related to the Sale of Future Royalties - Summary of Liability Related to Potential Future Royalties (Detail) - USD ($) $ in Thousands	12 Months Ended			46 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2015
Other Liabilities Disclosure [Abstract]
Liability related to the sale of future royalties—beginning balance	$ 120,471			$ 0
Proceeds from sale of future royalties				124,000
Payments from Nektar to RPI				(10,000)
Non-cash CIMZIA® and MIRCERA® royalty revenue	(22,058)	$ (21,937)	$ (22,055)	(76,841)
Non-cash interest expense recognized	20,619	20,888	$ 22,309	81,873
Liability related to the sale of future royalties – ending balance	$ 119,032	$ 120,471		$ 119,032

Commitments and Contingencies - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Aug. 14, 2015
Loss Contingencies [Line Items]
Royalty expense	$ 2,800,000	$ 3,400,000	$ 4,100,000
Purchase commitments related to contract manufacturing, clinical development and certain other items	5,400,000
Damage claim for unpaid licensing fee				$ 1,500,000
Indemnification Obligation [Member]
Loss Contingencies [Line Items]
Indemnification obligations, liabilities	0	$ 0
Merger and Acquisition Related Claims [Member]
Loss Contingencies [Line Items]
Obligations under Director and Officer Indemnifications per incident	1,500,000
Securities Related Claims [Member]
Loss Contingencies [Line Items]
Obligations under Director and Officer Indemnifications per incident	1,000,000
Non-Securities Related Claims [Member]
Loss Contingencies [Line Items]
Obligations under Director and Officer Indemnifications per incident	$ 500,000

Stockholders' Equity - Additional Information (Detail) - USD ($)			12 Months Ended
	Jun. 16, 2015	Jan. 28, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Class of Stock [Line Items]
Preferred stock, shares authorized			10,000,000	10,000,000
Preferred stock, par value			$ 0.0001	$ 0.0001
Preferred stock, shares designated			0	0
Preferred stock, shares issued			0	0
Preferred stock, shares outstanding			0	0
Proceeds from sale of common stock		$ 117,200,000
Common stock, shares authorized			300,000,000	300,000,000
Maximum 401(k) per employee, percentage of annual salary			60.00%
Compensation expense in connection with 401(k) retirement plan			$ 900,000	$ 900,000	$ 1,000,000
Severance payment period for executives			12 months
Severance payment period for employees			6 months
Cash severance payment for chief executive officer			24 months base salary plus annual target incentive pay
Employee Stock Purchase Plan [Member]
Class of Stock [Line Items]
Common stock, shares authorized			2,500,000
Percentage of purchase price of stock			85.00%
Maximum [Member]
Class of Stock [Line Items]
Matching 401(k) employer contribution, maximum amount			$ 3,000
2012 Performance Incentive Plan [Member]
Class of Stock [Line Items]
Additional new shares available for award grants	7,000,000
Share-based compensation plan's share limit reduction for every one restricted stock unit granted			1.5
2012 Performance Incentive Plan [Member] \| Maximum [Member]
Class of Stock [Line Items]
Number of common stock shares available for stock options grants			19,936,433
Stock options term under equity incentive plans			8 years
2012 Performance Incentive Plan [Member] \| Employee [Member]
Class of Stock [Line Items]
Service period for stock-based compensation award granted			4 years
2012 Performance Incentive Plan [Member] \| Director [Member]
Class of Stock [Line Items]
Service period for stock-based compensation award granted			1 year
Restricted Stock Units (RSU) [Member]
Class of Stock [Line Items]
Awards granted			1,306,000	0	0
Restricted Stock Units (RSU) [Member] \| Employee [Member]
Class of Stock [Line Items]
Service period for stock-based compensation award granted			3 years
Restricted Stock Units (RSU) [Member] \| Director [Member]
Class of Stock [Line Items]
Service period for stock-based compensation award granted			1 year
2000 Non-Officer Equity Incentive Plan [Member]
Class of Stock [Line Items]
Stock options term under equity incentive plans			8 years
Common Shares [Member]
Class of Stock [Line Items]
Sale of common stock, Shares		9,775,000		9,775,000
Underwriting commission and discounts		$ 7,500,000
Legal, accounting fees, filing fees and other offering expenses		$ 600,000
Common stock, shares reserved for issuance in equity compensation plans			27,744,597

Stockholders' Equity - Summarization of Common Stock Shares for Issuance Under Existing Equity Compensation Plans (Detail) shares in Thousands	Dec. 31, 2015 $ / shares shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of Securities to be Issued Upon Exercise of Outstanding Options & Vesting of RSUs	20,088
Weighted-Average Exercise Price of Outstanding Options \| $ / shares	$ 11.22
Number of Securities Remaining Available for Issuance Under Equity Compensation Plans (Excluding Securities Reflected in Column)	7,657
Equity Compensation Plans Approved by Security Holders [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of Securities to be Issued Upon Exercise of Outstanding Options & Vesting of RSUs	18,056
Weighted-Average Exercise Price of Outstanding Options \| $ / shares	$ 11.33
Number of Securities Remaining Available for Issuance Under Equity Compensation Plans (Excluding Securities Reflected in Column)	7,657
Equity Compensation Plans Not Approved by Security Holders [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of Securities to be Issued Upon Exercise of Outstanding Options & Vesting of RSUs	2,032
Weighted-Average Exercise Price of Outstanding Options \| $ / shares	$ 10.30
Number of Securities Remaining Available for Issuance Under Equity Compensation Plans (Excluding Securities Reflected in Column)	0

License and Collaboration Agreements - License, Collaboration and Other Revenue (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
License And Collaboration Agreements [Line Items]
License, collaboration and other revenue	$ 165,604	$ 153,289	$ 80,872
AstraZeneca AB [Member] \| MOVANTIKTM (NKTR-118) and MOVANTIKTM fixed-dose combination program (NKTR-119) [Member]
License And Collaboration Agreements [Line Items]
License, collaboration and other revenue	130,000	105,001	25,016
Roche [Member] \| PEGASYS and MIRCERA [Member]
License And Collaboration Agreements [Line Items]
License, collaboration and other revenue	12,816	12,845	18,382
Baxalta Incorporated [Member] \| ADYNOVATETM [Member]
License And Collaboration Agreements [Line Items]
License, collaboration and other revenue	10,694	10,258	1,702
Amgen, Inc. [Member] \| Neulasta [Member]
License And Collaboration Agreements [Line Items]
License, collaboration and other revenue	5,000	5,000	5,035
Bayer Healthcare LLC [Member] \| BAY41-6551 (Amikacin Inhale) [Member]
License And Collaboration Agreements [Line Items]
License, collaboration and other revenue	1,919	4,717	15,293
Affymax, Inc. [Member] \| OMONTYS [Member]
License And Collaboration Agreements [Line Items]
License, collaboration and other revenue	0	0	7,149
Other [Member]
License And Collaboration Agreements [Line Items]
License, collaboration and other revenue	$ 5,175	$ 15,468	$ 8,295

License and Collaboration Agreements - Additional Information (Detail) - USD ($)		1 Months Ended									3 Months Ended				12 Months Ended
	Sep. 16, 2014	Nov. 30, 2015	Aug. 31, 2015	Oct. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Nov. 30, 2013	Jun. 30, 2013	Feb. 29, 2012	Dec. 31, 2009	Mar. 31, 2015	Dec. 31, 2013	Dec. 31, 2010	Dec. 31, 2009	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2007	Jul. 31, 2016	Jul. 31, 2015
Deferred Revenue Arrangement [Line Items]
Potential future additional payments for development milestones															$ 113,300,000
AstraZeneca AB [Member] \| United States [Member]
Deferred Revenue Arrangement [Line Items]
Liability to AZ for DTC advertising payments											$ 10,000,000									$ 5,000,000
Reduction of revenue											(10,000,000)
AstraZeneca AB [Member] \| Scenario, Forecast [Member] \| United States [Member] \| Other Current Liabilities [Member]
Deferred Revenue Arrangement [Line Items]
Liability to AZ for DTC advertising payments																			$ 5,000,000
AstraZeneca AB [Member] \| MOVANTIKTM (NKTR-118) and MOVANTIKTM fixed-dose combination program (NKTR-119) [Member] \| Upfront Payment Arrangement in 2007 [Member]
Deferred Revenue Arrangement [Line Items]
Received upfront and milestone payments														$ 125,000,000
AstraZeneca AB [Member] \| Movantik Fixed-dose Combination Program [Member]
Deferred Revenue Arrangement [Line Items]
Contingent payments receivable based on development events regulatory to be pursued and completed solely by others															75,000,000
AstraZeneca AB [Member] \| MOVANTIK [Member]
Deferred Revenue Arrangement [Line Items]
Received upfront and milestone payments				$ 35,000,000			$ 70,000,000				$ 100,000,000
Deferred revenue															0
Percentage of post approval study costs to repay	33.00%
Maximum potential reduction in royalties	$ 35,000,000
AstraZeneca AB [Member] \| MOVANTIK [Member] \| United States [Member]
Deferred Revenue Arrangement [Line Items]
Potential reduction in U.S. royalty rate for repayment	2.00%
AstraZeneca AB [Member] \| MOVANTIK [Member] \| European Union [Member]
Deferred Revenue Arrangement [Line Items]
Received upfront and milestone payments			$ 40,000,000
Baxalta Incorporated [Member] \| ADYNOVATETM (Hemophilia) [Member]
Deferred Revenue Arrangement [Line Items]
Deferred revenue															0
Development milestones achieved		$ 10,000,000			$ 8,000,000
Baxalta Incorporated [Member] \| ADYNOVATETM (Hemophilia) [Member] \| European Union [Member]
Deferred Revenue Arrangement [Line Items]
Potential future additional payments for development milestones															10,000,000
Roche [Member] \| License Extension Option [Member]
Deferred Revenue Arrangement [Line Items]
Received upfront and milestone payments										$ 31,000,000
Roche [Member] \| PEGASYS [Member]
Deferred Revenue Arrangement [Line Items]
Deferred revenue															0
Roche [Member] \| MIRCERA [Member]
Deferred Revenue Arrangement [Line Items]
Deferred revenue															5,400,000
Consideration received for product delivered in 2013									$ 27,000,000			$ 18,600,000
Roche [Member] \| MIRCERA [Member] \| Performance-based Milestone Payments [Member]
Deferred Revenue Arrangement [Line Items]
Received upfront and milestone payments									22,000,000
Roche [Member] \| MIRCERA [Member] \| Upfront Payment Arrangement in 2007 [Member]
Deferred Revenue Arrangement [Line Items]
Received upfront and milestone payments									$ 5,000,000
Roche [Member] \| PEGASYS and MIRCERA [Member]
Deferred Revenue Arrangement [Line Items]
Deferred revenue															2,300,000
Amgen, Inc. [Member]
Deferred Revenue Arrangement [Line Items]
Received upfront and milestone payments													$ 50,000,000
Deferred revenue															24,200,000
Bayer Healthcare LLC [Member]
Deferred Revenue Arrangement [Line Items]
Potential future additional payments for development milestones															50,000,000
Deferred revenue															19,300,000
Payment made to Bayer for cost of Phase 3 clinical trial								$ 10,000,000
Bayer Healthcare LLC [Member] \| Performance-based Milestone Payments [Member]
Deferred Revenue Arrangement [Line Items]
Received upfront and milestone payments															30,000,000
Development milestone achieved in 2013																	$ 10,000,000
Bayer Healthcare LLC [Member] \| Upfront Payment Arrangement in 2007 [Member]
Deferred Revenue Arrangement [Line Items]
Received upfront and milestone payments																		$ 40,000,000
Ophthotech Corporation [Member] \| Fovista [Member]
Deferred Revenue Arrangement [Line Items]
Potential future additional payments for development milestones															9,500,000
Received upfront and milestone payments						$ 19,800,000
Deferred revenue															18,200,000
Potential future development milestones upon acceptance for review of regulatory approval															2,500,000
Affymax, Inc. [Member] \| OMONTYS [Member]
Deferred Revenue Arrangement [Line Items]
Deferred revenue recognized																	$ 6,700,000
Other [Member]
Deferred Revenue Arrangement [Line Items]
Potential future additional payments for development milestones															46,800,000
Deferred revenue															$ 14,500,000
Development milestones achieved																$ 9,000,000

Stock-Based Compensation - Stock-Based Compensation Expense (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock-based compensation	$ 19,669	$ 17,017	$ 17,708
Cost of Goods Sold [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock-based compensation	1,142	1,161	1,297
Research and Development Expense [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock-based compensation	9,207	7,528	7,910
General and Administrative Expense [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock-based compensation	$ 9,320	$ 8,328	$ 8,501

Stock-Based Compensation - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total unrecognized compensation costs	$ 58.5
Recognized over a weighted-average period	1 year 10 months 24 days
Dividend yield	0.00%	0.00%	0.00%
Stock Options [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Dividend yield				0.00%
Weighted-average grant-date fair value	$ 6.55	$ 6.50	$ 4.95
Total intrinsic value of options exercised	$ 20.5	$ 25.9	$ 4.5
Estimated fair value of options vested	$ 16.8	$ 15.2	$ 14.1
Restricted Stock Units (RSU) [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Awards granted	1,306,000	0	0

Stock-Based Compensation - Black-Scholes Option-Pricing Model Assumptions Used to Calculate Fair Value of Employee Stock Options (Detail)	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Average risk-free interest rate	1.60%	1.60%	0.90%
Dividend yield	0.00%	0.00%	0.00%
Average volatility factor	50.80%	51.60%	61.20%
Average weighted average expected life	5 years 3 months 18 days	5 years 2 months 12 days	5 years 2 months 12 days

Stock-Based Compensation - Stock Option Activity Under Equity Incentive Plans (Detail) - Stock Options [Member] $ / shares in Units, shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2015 USD ($) $ / shares shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of Shares, Outstanding, Beginning balance \| shares	21,995
Number of Shares, Options granted \| shares	1,746
Number of Shares, Options exercised \| shares	(3,937)
Number of Shares, Options forfeited and canceled \| shares	(1,022)
Number of Shares, Outstanding, Ending balance \| shares	18,782
Number of Shares, Vested and Expected to Vest \| shares	18,360
Number of Shares, Exercisable \| shares	12,222
Weighted-Average Exercise Price per Share, Outstanding, Beginning balance \| $ / shares	$ 10.50
Weighted-Average Exercise Price per Share, Options granted \| $ / shares	14.00
Weighted-Average Exercise Price per Share, Options exercised \| $ / shares	7.89
Weighted-Average Exercise Price per Share, Options forfeited and Canceled \| $ / shares	13.42
Weighted-Average Exercise Price per Share, Outstanding, Ending balance \| $ / shares	11.22
Weighted-Average Exercise Price per Share, Vested and expected to vest \| $ / shares	11.14
Weighted-Average Exercise Price per Share, Exercisable \| $ / shares	$ 9.89
Weighted-Average Remaining Contractual Life, Outstanding	4 years 8 months 1 day
Weighted-Average Remaining Contractual Life, Vested and expected to Vest	4 years 7 months 13 days
Weighted-Average Remaining Contractual Life, Exercisable	3 years 7 months 6 days
Aggregate Intrinsic Value, Outstanding \| $	$ 105,830
Aggregate Intrinsic Value, Vested and expected to Vest \| $	104,749
Aggregate Intrinsic Value, Exercisable \| $	$ 85,074

Stock-Based Compensation - Restricted Stock Unit Award Activity (Detail) - Restricted Stock Units (RSU) [Member] - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Units Issued, Beginning balance	0
Granted	1,306,000	0	0
Vested	0
Forfeited and canceled	0
Units Issued, Ending balance	1,306,000	0
Weighted average grant date fair value, granted	$ 15.30
Aggregate intrinsic value, Ending balance	$ 22,012

Income Taxes - Loss Before Provision (Benefit) for Income Taxes (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Income Tax Disclosure [Abstract]
Domestic	$ (81,931)	$ (56,414)	$ (161,068)
Foreign	1,260	1,986	1,300
Loss before provision (benefit) for income taxes	$ (80,671)	$ (54,428)	$ (159,768)

Income Taxes - Provision (Benefit) for Income Taxes (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Current:
Federal	$ 0	$ 0	$ 0
State	(1)	1	1
Foreign	529	(482)	1,838
Total Current	528	(481)	1,839
Deferred:
Federal	0	0	422
State	0	0	49
Foreign	(22)	(31)	(65)
Total Deferred	(22)	(31)	406
Provision (benefit) for income taxes	$ 506	$ (512)	$ 2,245

Income Taxes - Additional Information (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Income Taxes Disclosure [Line Items]
Statutory income tax rate	35.00%
Increase in valuation allowance	$ 17,300	$ 9,700
Valuation allowance related to stock-based compensation and exercises prior to the implementation of ASC 515 and 718	35,600	35,600
Deferred U.S. income taxes	0	0	$ 422
Income taxes have not been provided on a cumulative total	4,400
Income tax research credits	4,529	$ 2,933	$ 6,273
Federal orphan drug credits	$ 17,700
Federal orphan drug credits, expiration year	2026
Unrecognized tax benefits, period may increase or decrease due to tax examination	Next twelve months
Federal [Member]
Income Taxes Disclosure [Line Items]
Net operating loss carryforward for income tax	$ 1,223,600
Net operating loss carryforward, expiration year	2018
Income tax research credits	$ 45,000
Income tax research credits, expiration year	2019
State [Member]
Income Taxes Disclosure [Line Items]
Net operating loss carryforward for income tax	$ 489,600
Net operating loss carryforward, expiration year	2016
Income tax research credits	$ 24,600

Income Taxes - Income Tax Provision Related to Continuing Operations (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
U.S. federal provision (benefit)
At statutory rate	$ (28,235)	$ (19,050)	$ (55,919)
State taxes	(1)	1	50
Change in valuation allowance	22,210	11,831	55,042
Non-cash interest expense on liability related to sale of future royalties	7,217	7,311	7,808
Stock-based compensation	674	2,832	271
Foreign tax inclusion	1,773	0	0
Foreign tax differential	(7)	(17)	(20)
Research credits	(4,529)	(2,933)	(6,273)
Other	1,404	(487)	1,286
Provision (benefit) for income taxes	$ 506	$ (512)	$ 2,245

Income Taxes - Significant Components of Deferred Tax Assets and Liabilities (Detail) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Deferred tax assets:
Net operating loss carryforwards	$ 447,761	$ 423,776
Research and other credits	70,258	66,666
Deferred revenue	29,658	29,758
Stock-based compensation	22,832	21,948
Capitalized research expenses	12,440	14,795
Sale of future royalties	12,319	20,153
Reserves and accruals	8,309	8,288
Property, plant and equipment	6,451	8,264
Other	3,158	2,218
Deferred tax assets before valuation allowance	613,186	595,866
Valuation allowance for deferred tax assets	(612,996)	(595,690)
Total deferred tax assets	190	176
Total deferred tax liabilities	0	0
Net deferred tax assets	$ 190	$ 176

Income Taxes - Unrecognized Tax Benefits (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Income Tax Contingency [Line Items]
Beginning balance	$ 27,522	$ 16,363	$ 14,067
Reductions	0	0	0
Reductions	(11,110)	(742)	0
Settlements	0	0	0
Lapses in statute of limitations	0	0	0
Ending balance	17,384	27,522	16,363
Federal [Member]
Income Tax Contingency [Line Items]
Tax positions related to current year, Additions	529	502	477
Tax positions related to prior year, Additions	0	0	636
State [Member]
Income Tax Contingency [Line Items]
Tax positions related to current year, Additions	443	6,141	381
Tax positions related to prior year, Additions	0	5,258	0
Foreign [Member]
Income Tax Contingency [Line Items]
Tax positions related to prior year, Additions	$ 0	$ 0	$ 802

Segment Reporting - Additional Information (Detail) $ in Thousands	12 Months Ended
	Dec. 31, 2015 USD ($) Segment	Dec. 31, 2014 USD ($)	Dec. 31, 2013
Segment Reporting Information [Line Items]
Number of operating business segment \| Segment	1
Property, plant and equipment, net	$ 71,336	$ 70,368
United States [Member]
Segment Reporting Information [Line Items]
Property, plant and equipment, net	$ 54,200	$ 53,300
Percentage of net book value of property and equipment	76.00%	76.00%
India [Member]
Segment Reporting Information [Line Items]
Property, plant and equipment, net	$ 6,000	$ 6,700
Percentage of net book value of property and equipment	8.00%	10.00%
Germany and Netherlands [Member]
Segment Reporting Information [Line Items]
Property, plant and equipment, net	$ 11,100	$ 10,400
Percentage of net book value of property and equipment	16.00%	14.00%
Revenue [Member] \| AstraZeneca [Member] \| Customer Concentration Risk [Member]
Segment Reporting Information [Line Items]
Percentage revenue from clients	57.00%	52.00%	17.00%
Revenue [Member] \| UCB [Member] \| Customer Concentration Risk [Member]
Segment Reporting Information [Line Items]
Percentage revenue from clients	13.00%	16.00%	21.00%
Revenue [Member] \| Roche [Member] \| Customer Concentration Risk [Member]
Segment Reporting Information [Line Items]
Percentage revenue from clients		11.00%	28.00%
Revenue [Member] \| Bayer [Member] \| Customer Concentration Risk [Member]
Segment Reporting Information [Line Items]
Percentage revenue from clients			10.00%

Segment Reporting - Revenue by Geographic Area (Detail) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Revenue by geographic area
Total revenue	$ 39,370	$ 59,952	$ 22,661	$ 108,801	$ 19,551	$ 132,871	$ 28,513	$ 19,771	$ 230,784	$ 200,707	$ 148,921
United States [Member]
Revenue by geographic area
Total revenue									40,400	32,514	42,535
European [Member]
Revenue by geographic area
Total revenue									$ 190,384	$ 168,193	$ 106,386

Selected Quarterly Financial Data - Quarterly Financial Data (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Income Statement [Abstract]
Product sales	$ 13,973	$ 7,240	$ 10,968	$ 7,974	$ 7,460	$ 6,096	$ 5,802	$ 5,795	$ 40,155	$ 25,152	$ 44,846
Total revenue	39,370	59,952	22,661	108,801	19,551	132,871	28,513	19,771	230,784	200,707	148,921
Cost of goods sold	8,364	6,760	10,534	8,444	6,298	9,220	5,108	7,907	34,102	28,533	38,509
Research and development expenses	47,135	43,229	45,412	47,011	38,494	34,200	36,702	38,338	182,787	147,734	190,010
Operating income (loss)	(29,364)	419	(43,469)	43,043	(37,488)	80,321	(22,916)	(36,402)	(29,371)	(16,485)	(120,130)
Net income (loss)	$ (54,137)	$ (8,203)	$ (52,657)	$ 33,820	$ (45,683)	$ 70,605	$ (32,637)	$ (46,201)	$ (81,177)	$ (53,916)	$ (162,013)
Net income (loss) per share
Basic	$ (0.40)	$ (0.06)	$ (0.40)	$ 0.26	$ (0.35)	$ 0.55	$ (0.26)	$ (0.37)
Diluted	$ (0.40)	$ (0.06)	$ (0.40)	$ 0.25	$ (0.35)	$ 0.53	$ (0.26)	$ (0.37)

Consolidated Statements of Stockholders' Equity (Deficit) (Parenthetical) $ in Thousands	12 Months Ended
	Dec. 31, 2014 USD ($)
Statement Of Stockholders Equity [Abstract]
Stock issuance costs	$ 617

Consolidated Statements of Cash Flows (Parenthetical)	Dec. 31, 2015
7.75% Senior Secured Notes [Member]
Senior secured notes, interest rate	7.75%
12% Senior Secured Notes [Member]
Senior secured notes, interest rate	12.00%