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Cover Page - shares	6 Months Ended
Cover Page - shares	Jun. 30, 2020	Jul. 31, 2020
Cover [Abstract]
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Jun. 30, 2020
Document Transition Report	false
Entity File Number	0-24006
Entity Registrant Name	NEKTAR THERAPEUTICS
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	94-3134940
Entity Address, Address Line One	455 Mission Bay Boulevard South
Entity Address, City or Town	San Francisco
Entity Address, State or Province	CA
Entity Address, Postal Zip Code	94158
City Area Code	415
Local Phone Number	482-5300
Title of 12(b) Security	Common Stock, $0.0001 par value
Trading Symbol	NKTR
Security Exchange Name	NASDAQ
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding		178,899,759
Amendment Flag	false
Document Fiscal Year Focus	2020
Document Fiscal Period Focus	Q2
Entity Central Index Key	0000906709
Current Fiscal Year End Date	--12-31

Condensed Consolidated Balance Sheets - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Current assets:
Cash and cash equivalents	$ 58,206	$ 96,363
Short-term investments	980,191	1,228,499
Accounts receivable	47,245	36,802
Inventory	12,584	12,665
Advance payments to contract manufacturers	15,972	31,834
Other current assets	37,770	15,387
Total current assets	1,151,968	1,421,550
Long-term investments	172,166	279,119
Property, plant and equipment, net	61,372	65,665
Operating lease right-of-use assets	131,458	134,177
Goodwill	76,501	76,501
Other assets	1,413	344
Total assets	1,594,878	1,977,356
Current liabilities:
Senior secured notes, net and interest payable (see Note 1)	0	252,891
Accounts payable	19,246	19,234
Accrued compensation	22,548	11,467
Accrued clinical trial expenses	42,794	32,626
Accrued contract manufacturing expenses	11,050	7,304
Other accrued expenses	11,424	12,338
Operating lease liabilities, current portion	15,139	12,516
Deferred revenue, current portion	1,757	5,517
Total current liabilities	123,958	353,893
Operating lease liabilities, less current portion	141,633	142,730
Liability related to the sale of future royalties, net	68,284	72,020
Deferred revenue, less current portion	2,524	2,554
Other long-term liabilities	2,239	768
Total liabilities	338,638	571,965
Commitments and contingencies
Stockholders’ equity:
Preferred stock, $0.0001 par value; 10,000 shares authorized; no shares designated or outstanding at June 30, 2020 or December 31, 2019	0	0
Common stock, $0.0001 par value; 300,000 shares authorized; 178,810 shares and 176,505 shares outstanding at June 30, 2020 and December 31, 2019, respectively	18	17
Capital in excess of par value	3,338,876	3,271,097
Accumulated other comprehensive income (loss)	715	(1,005)
Accumulated deficit	(2,083,369)	(1,864,718)
Total stockholders’ equity	1,256,240	1,405,391
Total liabilities and stockholders’ equity	$ 1,594,878	$ 1,977,356
Preferred stock, par value (in dollars per share)	$ 0.0001	$ 0.0001
Preferred stock, shares authorized (in shares)	10,000,000	10,000,000
Preferred stock, shares designated (in shares)	0	0
Preferred stock, shares outstanding (in shares)	0	0
Common stock, par value (in dollars per share)	$ 0.0001	$ 0.0001
Common stock, shares authorized (in shares)	300,000,000	300,000,000
Common stock, shares outstanding (in shares)	178,810,000	176,505,000

Condensed Consolidated Statements of Operations - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Revenue:
Total revenue	$ 48,847	$ 23,315	$ 99,420	$ 51,537
Operating costs and expenses:
Cost of goods sold	5,773	5,018	9,584	10,458
Research and development	96,436	106,686	205,423	225,149
General and administrative	24,347	22,581	50,564	47,587
Impairment of assets and other costs for terminated program	0	0	45,189	0
Total operating costs and expenses	126,556	134,285	310,760	283,194
Loss from operations	(77,709)	(110,970)	(211,340)	(231,657)
Non-operating income (expense):
Interest expense	(647)	(5,231)	(6,851)	(10,457)
Non-cash interest expense on liability related to sale of future royalties	(6,691)	(5,975)	(13,659)	(12,040)
Interest income and other income (expense), net	5,191	11,989	13,543	24,472
Total non-operating income (expense), net	(2,147)	783	(6,967)	1,975
Loss before provision for income taxes	(79,856)	(110,187)	(218,307)	(229,682)
Provision for income taxes	144	99	344	236
Net loss	$ (80,000)	$ (110,286)	$ (218,651)	$ (229,918)
Basic and diluted net loss per share (in dollars per share)	$ (0.45)	$ (0.63)	$ (1.23)	$ (1.32)
Weighted average shares outstanding used in computing basic and diluted net loss per share (in shares)	178,327	174,549	177,755	174,206
Product sales
Revenue:
Total revenue	$ 5,485	$ 4,346	$ 8,929	$ 8,744
Royalty revenue
Revenue:
Total revenue	9,403	7,343	19,122	18,733
Non-cash royalty revenue related to sale of future royalties
Revenue:
Total revenue	7,684	9,091	17,579	17,321
License, collaboration and other revenue
Revenue:
Total revenue	$ 26,275	$ 2,535	$ 53,790	$ 6,739

Condensed Consolidated Statements of Comprehensive Loss - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Statement of Comprehensive Income [Abstract]
Net loss	$ (80,000)	$ (110,286)	$ (218,651)	$ (229,918)
Other comprehensive income (loss):
Net unrealized gain on available-for-sale investments	7,688	2,197	2,567	6,882
Net foreign currency translation gain (loss)	(96)	108	(847)	143
Other comprehensive income	7,592	2,305	1,720	7,025
Comprehensive loss	$ (72,408)	$ (107,981)	$ (216,931)	$ (222,893)

- Definition

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

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+ Details

- Definition

Amount after tax and reclassification adjustments of other comprehensive income (loss).

+ References

+ Details

Condensed Consolidated Statements of Stockholders' Equity - USD ($) $ in Thousands	Total	Common Shares	Capital in Excess of Par Value	Accumulated Other Comprehensive Income (Loss)	Accumulated Deficit
Beginning balance (in shares) at Dec. 31, 2018		173,530,000
Beginning balance at Dec. 31, 2018	$ 1,717,575	$ 17	$ 3,147,925	$ (6,316)	$ (1,424,051)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Shares issued under equity compensation plans (in shares)		698,000
Shares issued under equity compensation plans	5,463		5,463
Stock-based compensation	25,385		25,385
Comprehensive loss	(114,912)			4,720	(119,632)
Ending balance (in shares) at Mar. 31, 2019		174,228,000
Ending balance at Mar. 31, 2019	1,633,511	$ 17	3,178,773	(1,596)	(1,543,683)
Beginning balance (in shares) at Dec. 31, 2018		173,530,000
Beginning balance at Dec. 31, 2018	$ 1,717,575	$ 17	3,147,925	(6,316)	(1,424,051)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Shares issued under equity compensation plans (in shares)	115,000
Comprehensive loss	$ (222,893)
Ending balance (in shares) at Jun. 30, 2019		174,966,000
Ending balance at Jun. 30, 2019	1,557,155	$ 17	3,210,398	709	(1,653,969)
Beginning balance (in shares) at Mar. 31, 2019		174,228,000
Beginning balance at Mar. 31, 2019	$ 1,633,511	$ 17	3,178,773	(1,596)	(1,543,683)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Shares issued under equity compensation plans (in shares)	95,000	738,000
Shares issued under equity compensation plans	$ 7,841		7,103
Stock-based compensation	24,522		24,522
Comprehensive loss	(107,981)			2,305	(110,286)
Ending balance (in shares) at Jun. 30, 2019		174,966,000
Ending balance at Jun. 30, 2019	1,557,155	$ 17	3,210,398	709	(1,653,969)
Beginning balance (in shares) at Dec. 31, 2019		176,505,000
Beginning balance at Dec. 31, 2019	1,405,391	$ 17	3,271,097	(1,005)	(1,864,718)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Shares issued under equity compensation plans (in shares)		1,358,000
Shares issued under equity compensation plans	11,347		11,347
Stock-based compensation	24,211		24,211
Comprehensive loss	(144,523)			(5,872)	(138,651)
Ending balance (in shares) at Mar. 31, 2020		177,863,000
Ending balance at Mar. 31, 2020	1,296,426	$ 17	3,306,655	(6,877)	(2,003,369)
Beginning balance (in shares) at Dec. 31, 2019		176,505,000
Beginning balance at Dec. 31, 2019	$ 1,405,391	$ 17	3,271,097	(1,005)	(1,864,718)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Shares issued under equity compensation plans (in shares)	49,000
Comprehensive loss	$ (216,931)
Ending balance (in shares) at Jun. 30, 2020		178,810,000
Ending balance at Jun. 30, 2020	1,256,240	$ 18	3,338,876	715	(2,083,369)
Beginning balance (in shares) at Mar. 31, 2020		177,863,000
Beginning balance at Mar. 31, 2020	$ 1,296,426	$ 17	3,306,655	(6,877)	(2,003,369)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Shares issued under equity compensation plans (in shares)	0	947,000
Shares issued under equity compensation plans	$ 7,826	$ 1	7,825
Stock-based compensation	24,396		24,396
Comprehensive loss	(72,408)			7,592	(80,000)
Ending balance (in shares) at Jun. 30, 2020		178,810,000
Ending balance at Jun. 30, 2020	$ 1,256,240	$ 18	$ 3,338,876	$ 715	$ (2,083,369)

- Definition

Total of all stockholders' equity (deficit) items, net of receivables from officers, directors, owners, and affiliates of the entity which are attributable to the parent. The amount of the economic entity's stockholders' equity attributable to the parent excludes the amount of stockholders' equity which is allocable to that ownership interest in subsidiary equity which is not attributable to the parent (noncontrolling interest, minority interest). This excludes temporary equity and is sometimes called permanent equity.

+ References + Details

Condensed Consolidated Statements of Cash Flows (Unaudited) - USD ($)	6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019
Cash flows from operating activities:
Net loss	$ (218,651,000)	$ (229,918,000)
Adjustments to reconcile net loss to net cash used in operating activities:
Non-cash royalty revenue related to sale of future royalties	(17,579,000)	(17,321,000)
Non-cash interest expense on liability related to sale of future royalties	13,659,000	12,040,000
Stock-based compensation	48,607,000	49,907,000
Depreciation and amortization	7,692,000	6,132,000
Impairment of advance payments to contract manufacturers and equipment for terminated program	20,351,000	0
Accretion of premiums (discounts), net and other non-cash transactions	(782,000)	(6,329,000)
Changes in operating assets and liabilities:
Accounts receivable	(10,443,000)	5,914,000
Inventory	81,000	(1,807,000)
Operating leases, net	4,245,000	8,415,000
Other assets	(27,214,000)	15,818,000
Accounts payable	425,000	3,480,000
Accrued compensation	12,469,000	9,773,000
Other accrued expenses	8,952,000	15,794,000
Deferred revenue	(3,790,000)	(6,715,000)
Net cash used in operating activities	(161,978,000)	(134,817,000)
Cash flows from investing activities:
Purchases of investments	(543,631,000)	(603,702,000)
Maturities of investments	860,330,000	634,145,000
Sales of investments	41,700,000	0
Purchases of property, plant and equipment	(3,594,000)	(17,291,000)
Net cash provided by investing activities	354,805,000	13,152,000
Cash flows from financing activities:
Proceeds from shares issued under equity compensation plans	19,120,000	12,200,000
Repayment of senior notes	(250,000,000)	0
Net cash provided by (used in) financing activities	(230,880,000)	12,200,000
Effect of foreign exchange rates on cash and cash equivalents	(104,000)	(16,000)
Net decrease in cash and cash equivalents	(38,157,000)	(109,481,000)
Cash and cash equivalents at beginning of period	96,363,000	194,905,000
Cash and cash equivalents at end of period	58,206,000	85,424,000
Supplemental disclosures of cash flow information:
Cash paid for interest	9,742,000	9,455,000
Operating lease right-of-use asset recognized in exchange for lease liabilities	$ 2,133,000	$ 1,289,000

Organization and Summary of Significant Accounting Policies	6 Months Ended
	Jun. 30, 2020
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Organization and Summary of Significant Accounting Policies	Organization and Summary of Significant Accounting Policies Organization We are a research-based biopharmaceutical company headquartered in San Francisco, California and incorporated in Delaware. We are developing a pipeline of drug candidates that utilize our advanced polymer conjugate technology platforms, which are designed to enable the development of new molecular entities that target known mechanisms of action. Our research and development pipeline of new investigational drugs includes investigational treatments for cancer and autoimmune disease. 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 June 30, 2020, we had approximately $1.2 billion in cash and investments in marketable securities. On April 13, 2020, we repaid the principal and accrued interest of our senior notes totaling $254.8 million, as described further below. Basis of Presentation and Principles of Consolidation Our consolidated financial statements include the financial position, results of operations and cash flows of our wholly-owned subsidiaries: Inheris Biopharma, Inc. (Inheris), Nektar Therapeutics (India) Private Limited (Nektar India) and Nektar Therapeutics UK Limited. We have eliminated all intercompany accounts and transactions in consolidation. We prepared our Condensed Consolidated Financial Statements following the requirements of the Securities and Exchange Commission (SEC) for interim reporting. As permitted under those rules, we may condense or omit certain footnotes or other financial information that are normally required by U.S. generally accepted accounting principles (GAAP) for annual periods. In the opinion of management, these financial statements include all normal and recurring adjustments that we consider necessary for the fair presentation of our financial position and operating results. Our Condensed 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. We include translation gains and losses in accumulated other comprehensive income (loss) in the stockholders’ equity section of our Condensed Consolidated Balance Sheets. To date, such cumulative currency translation adjustments have not been significant to our consolidated financial position. Our comprehensive loss consists of our net loss plus our foreign currency translation gains and losses and unrealized holding gains and losses on available-for-sale securities. There were no significant reclassifications out of accumulated other comprehensive income (loss) to the statements of operations during the three and six months ended June 30, 2020 and 2019. The accompanying Condensed Consolidated Financial Statements are unaudited. The Condensed Consolidated Balance Sheet data as of December 31, 2019 was derived from the audited consolidated financial statements which are included in our Annual Report on Form 10-K for the year ended December 31, 2019 filed with the SEC on February 28, 2020. The information included in this Quarterly Report on Form 10-Q should be read in conjunction with the consolidated financial statements and the accompanying notes to those financial statements included in our Annual Report on Form 10-K for the year ended December 31, 2019. Revenue, expenses, assets, and liabilities can vary during each quarter of the year. The results and trends in these interim Condensed Consolidated Financial Statements are not necessarily indicative of the results to be expected for the full year or any other period. Use of Estimates The preparation of consolidated financial statements in conformity with 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. The full extent to which the COVID-19 pandemic will directly or indirectly impact our business, results of operations and financial condition, including sales, expenses, reserves and allowances, manufacturing, clinical trials, research and development costs and employee-related amounts, will depend on future developments that are highly uncertain, including as a result of new information that may emerge concerning the COVID-19 pandemic and the actions taken to contain it or treat COVID-19, as well as the economic impact on local, regional, national and international customers and markets. We consider the effects of the COVID-19 pandemic in developing our estimates. Actual results could differ materially from those estimates and assumptions. As appropriate, we assess our estimates each period, update them to reflect current information and generally recognize any changes in such estimates in the period first identified. Reclassifications In December 2019, the FASB issued ASU 2019-12 - Income Taxes (Topic 740): Simplifying the Accounting for Income Taxes (ASU 2019-12). ASU 2019-12 created an exception to the incremental approach for intraperiod tax allocation when there is a loss from continuing operations and income or a gain from other items (for example, discontinued operations or other comprehensive income). Under the historical guidance, in this situation, an entity would record an income tax provision from other items, such as unrealized gains on available-for-sale securities reported in other comprehensive income, with an offsetting income tax benefit in continuing operations. Under ASU 2019-12, an entity would record no income tax provision. We elected to adopt ASU 2019-12 effective January 1, 2019 on a prospective basis in accordance with the guidance. Because we reported a net loss and unrealized gains on available-for-sale securities during 2019 and accordingly recorded a tax provision pursuant to the legacy guidance, we have recast such results from previously reported amounts. As a result, we eliminated the tax benefit in continuing operations and tax provision in other comprehensive income (loss), which totaled $0.4 million and $1.5 million for three and six months ended June 30, 2019. Additionally, 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. Segment Information We operate in one business segment which focuses on applying our technology platform to develop novel drug candidates. 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. Significant Concentrations Our customers are primarily pharmaceutical and biotechnology companies that are located in the U.S. and Europe and with whom we have multi-year arrangements. Our accounts receivable balance contains billed and unbilled trade receivables from product sales, milestones (to the extent that they have been achieved and are due from the counterparty), other contingent payments and royalties, as well as reimbursable costs from collaborative research and development agreements. As of June 30, 2020, our accounts receivable includes $13.3 million under customer contracts from our collaboration partners and $33.9 million for unbilled net expense reimbursements from our collaboration partner Bristol-Myers Squibb Company (BMS). As of June 30, 2020, we also recorded a contract asset of $25.0 million, which we report in other current assets on our Condensed Consolidated Balance Sheet, from our collaboration partner BMS for the first patient, first visit for the registrational adjuvant melanoma trial (see Note 6 for additional information). As of December 31, 2019, our accounts receivable included $12.8 million from customer contracts and $24.0 million for unbilled net expense reimbursements from BMS. We generally do not require collateral from our customers. We perform a regular review of our customers’ credit risk and payment histories, including payments made after period end. Historically, we have not experienced credit losses from our accounts receivable. We have not recorded a reserve for credit losses at June 30, 2020 or December 31, 2019. We are dependent on our suppliers and contract manufacturers to provide raw materials and drugs 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. For our available-for-sale securities, we have significant concentrations of issuers in the banking and financial services, automotive and food and beverage industries. While our investment policy requires that we only invest in highly-rated securities and limit our exposure to any single issuer, the COVID-19 pandemic may materially affect the financial conditions of issuers. Additionally, pursuant to our investment policy, we may sell securities before maturity if the issuer’s credit rating has been downgraded below our minimum credit rating requirements, which may result in a loss on the sale. As a result of the COVID-19 pandemic, we have begun to see an increase in credit downgrades for certain of our securities. Accordingly, if the COVID-19 pandemic or other factors result in downgrades below our minimum credit rating requirements and if we decide to sell these securities, we may experience losses on such sales. Senior Secured Notes On October 5, 2015, we completed the sale and issuance of $250.0 million in aggregate principal amount of 7.75% senior secured notes due 2020 (the Notes). The Notes were secured by a first-priority lien on substantially all of our assets (except our right-of-use assets) and bore 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. Interest was calculated based on actual days outstanding over a 360 days year. The Notes were to mature on October 5, 2020, at which time the outstanding principal would be due and payable. On April 13, 2020, we redeemed the Notes at par and therefore repaid the principal of $250.0 million and accrued interest of $4.8 million. As a result of the redemption and repayment, the liens discussed above were terminated. Collaborative Arrangements We enter into collaboration arrangements with pharmaceutical and biotechnology collaboration partners, under which we may grant licenses to our collaboration partners to further develop and commercialize one of our proprietary drug candidates, either alone or in combination with the collaboration partners’ compounds, or grant licenses to partners to use our technology to research and develop their own proprietary drug candidates. We may also perform research, development, manufacturing and supply activities under our collaboration agreements. Consideration under these contracts may include an upfront payment, development and regulatory milestones and other contingent payments, expense reimbursements, royalties based on net sales of approved drugs, and commercial sales milestone payments. Additionally, these contracts may provide options for the customer to purchase our proprietary PEGylation materials, drug candidates or additional contract research and development services under separate contracts. When we enter into collaboration agreements, we assess whether the arrangements fall within the scope of ASC 808, Collaborative Arrangements (ASC 808) based on whether the arrangements involve joint operating activities and whether both parties have active participation in the arrangement and are exposed to significant risks and rewards of the arrangement. To the extent that the arrangement falls within the scope of ASC 808, we assess whether the payments between us and our collaboration partner fall within the scope of other accounting literature. If we conclude that payments from the collaboration partner to us represent consideration from a customer, such as license fees and contract research and development activities, we account for those payments within the scope of ASC 606, Revenue from Contracts with Customers (ASC 606). However, if we conclude that our collaboration partner is not a customer for certain activities and associated payments, such as for certain collaborative research, development, manufacturing and commercial activities, we present such payments as a reduction of research and development expense or general and administrative expense, based on where we present the underlying expense. Revenue Recognition For elements of those arrangements that we determine should be accounted for under ASC 606, we assess which activities in our collaboration agreements are performance obligations that should be accounted for separately and determine the transaction price of the arrangement, which includes the assessment of the probability of achievement of future milestones and other potential consideration. For arrangements that include multiple performance obligations, such as granting a license or performing contract research and development activities or participation on joint steering or other committees, we allocate upfront and milestone payments under a relative standalone selling price method. Accordingly, we develop assumptions that require judgment to determine the standalone selling price for each performance obligation identified in the contract. These key assumptions may include revenue forecasts, clinical development timelines and costs, discount rates and probabilities of clinical and regulatory success. Product Sales Product sales are primarily derived from manufacturing and supply agreements with our customers. We have assessed our current manufacturing and supply arrangements and have generally determined that they provide the customer an option to purchase our proprietary PEGylation materials. Accordingly, we treat each purchase order as a discrete exercise of the customer’s option (i.e. a separate contract) rather than as a component of the overall arrangement. The pricing for the manufacturing and supply is generally at a fixed price and may be subject to annual producer price index (PPI) adjustments. We invoice and recognize product sales when title and risk of loss pass to the customer, which generally occurs upon shipment. Customer payments are generally due 30 days from receipt of invoice. We test our products for adherence to technical specifications before shipment; accordingly, 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. For arrangements that include sales-based royalties, including commercial milestone payments based on the level of sales, we have concluded that the license is the predominant item to which the royalties relate. Accordingly, we recognize royalty revenue, including for our non-cash royalties, when the underlying sales occur based on our best estimates of sales of the drugs. Our partners generally pay royalties or commercial milestones after the end of the calendar quarter in accordance with contractual terms. We present commercial milestone payments within license, collaboration and other revenue. License, Collaboration and other Revenue License Grants: For collaboration arrangements that include a grant of a license to our intellectual property, we consider whether the license grant is distinct from the other performance obligations included in the arrangement. Generally, we would conclude that the license is distinct if the customer is able to benefit from the license with the resources available to it. For licenses that are distinct, we recognize revenues from nonrefundable, upfront payments and other consideration allocated to the license when the license term has begun and we have provided all necessary information regarding the underlying intellectual property to the customer, which generally occurs at or near the inception of the arrangement. Milestone Payments: At the inception of the arrangement and at each reporting date thereafter, we assess whether we should include any milestone payments or other forms of variable consideration in the transaction price, based on whether a significant reversal of revenue previously recognized is not probable upon resolution of the uncertainty. Since milestone payments may become payable to us upon the initiation of a clinical study, filing for or receipt of regulatory approval or the first commercial sale of a product, we review the relevant facts and circumstances to determine when we should update the transaction price, which may occur before the triggering event. When we do update the transaction price for milestone payments, we allocate it on a relative standalone selling price basis and record revenue on a cumulative catch-up basis, which results in recognizing revenue for previously satisfied performance obligations in such period. If we update the transaction price before the triggering event, we recognize the increase in the transaction price as a contract asset. Our partners generally pay development milestones subsequent to achievement of the triggering event. Research and Development Services: For amounts allocated to our research and development obligations in a collaboration arrangement, we recognize revenue over time using a proportional performance model, representing the transfer of goods or services as we perform activities over the term of the agreement. 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. Where we perform research and development activities under a joint development collaboration, such as our collaboration with BMS, we record the cost reimbursement from our partner as a reduction to research and development expense when reimbursement amounts are due to us under the agreement. We record an accrued expense 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 estimated activities performed by our third parties. We may also accrue expenses based on the total estimated cost of the treatment phase on a per patient basis and 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. We record an accrued expense for the estimated costs of our contract manufacturing 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 include upfront payments and milestone payments, which depend on factors such as the achievement of the completion of certain stages of the manufacturing process. For purposes of recognizing expense, we assess whether we consider the production process is sufficiently defined such that the resulting product can be considered the delivery of a good, as evidenced by predictive or contractually required yields in the production process or payment terms based on the actual yield, or the delivery of a service, where processes and yields are developing and less certain. If we consider the process to be the delivery of a good, we recognize expense when the drug product is delivered, or we otherwise bear risk of loss. If we consider the process to be the delivery of a service, we recognize expense based on our best estimates of the contract manufacturer’s progress towards completion of the stages in the contracts. We recognize and amortize upfront payments and accrue liabilities based on the specific terms of each arrangement. Certain arrangements may provide upfront payments for certain stages of the arrangement and milestone payments for the completion of certain stages, and, accordingly, we may record advance payments for services that have not been completed or goods not delivered and liabilities for stages where the contract manufacturer is entitled to a milestone payment. We capitalize advance payments for goods or services that will be used or rendered for future research and development activities and recognize expense as the related goods are delivered or services 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. We generally consider such increases or decreases in cost as changes in estimates and reflect them in research and development expenses in the period identified. Impairment of Assets and Other Costs for Terminated Program On January 14, 2020, the joint FDA Anesthetic Drug Products Advisory Committee and Drug Safety and Risk Management Committee did not recommend approval of our NDA for NKTR-181. As a result, we withdrew our NDA and decided to make no further investments in this program. On February 26, 2020, the Audit Committee of our Board of Directors approved management’s plan for the wind-down of Inheris and the NKTR-181 program. As a result, in the three months ended March 31, 2020, we wrote off $19.7 million of advance payments to contract manufacturers for commercial batches of NKTR-181. We also incurred $25.5 million of additional costs, primarily for non-cancellable commitments to our contract manufacturers and certain severance costs. We present these costs in the Impairment of assets and other costs for terminated program line in our Condensed Consolidated Statement of Operations. We did not incur any substantial costs related to the wind-down of Inheris and the NKTR-181 program in the three months ended June 30, 2020. Income Taxes For the three and six months ended June 30, 2020 and 2019, our income tax expense primarily results from taxable income in our Nektar India subsidiary. We have fully reserved our U.S. federal deferred tax assets generated from our net operating losses, as we believe it is not more likely than not that the benefit will be realized. Coronavirus Aid, Relief and Economic Security Act In March 2020, the U.S. government enacted the Coronavirus Aid, Relief, and Economic Security Act, or CARES Act, which includes modifications to the limitation on business interest expense and net operating loss provisions and provides a payment delay of employer payroll taxes during 2020 after the date of enactment. We do not expect that the CARES Act will have a material effect on our results of operations or financial position. Recently Adopted Accounting Pronouncements On January 1, 2020, we adopted Accounting Standards Update 2018-18: Clarifying the Interaction between Topic 808 and Topic 606 (ASU 2018-18). The guidance clarifies that certain transactions between collaborative arrangement participants should be accounted for as revenue under ASC 606 when the collaborative arrangement participant is a customer for a promised good or service that is distinct within the collaborative arrangement. The guidance also precludes entities from presenting amounts related to transactions with a collaborative arrangement participant that is not a customer as revenue, unless those transactions are directly related to third-party sales. ASU 2018-18 is applied retrospectively to January 1, 2018, when we adopted ASC 606. Our adoption of ASU 2018-18 did not materially affect our revenue recognition. On January 1, 2020, we adopted ASU 2016-13: Financial Instruments - Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments. The guidance modifies the measurement and recognition of credit losses for most financial assets and certain other instruments. The amendment updates the guidance for measuring and recording credit losses on financial assets measured at amortized cost by replacing the “incurred loss” model with an “expected loss” model. As a result of adoption, we present these financial assets, which include our accounts receivable and available-for-sale debt securities, at the net amount we expect to collect. The amendment also requires that we record credit losses related to available-for-sale debt securities as an allowance through net income rather than reducing the carrying amount under the historical, other-than-temporary-impairment model. Our adoption of ASU 2016-13 did not materially affect our Condensed Consolidated Financial Statements.

License and Collaboration Agreements

6 Months Ended

Jun. 30, 2020

Organization, Consolidation and Presentation of Financial Statements [Abstract]

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 milestone payments, and payments for the manufacture and supply of our proprietary PEGylation materials and/or reimbursement for research and development activities. We generally include our costs of performing these services in research and development expense, except for costs for product sales to our collaboration partners which we include in cost of goods sold. We analyze our agreements to determine whether we should account for the agreements within the scope of ASC 808, and, if so, we analyze whether we should account for any elements under ASC 606.

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


		Three months ended June 30,						Six months ended June 30,
Partner	Drug or Drug Candidate	2020		2019		2020		2019
Bristol-Myers Squibb Company	Bempegaldesleukin	$	25,000	$	—	$	50,000	$	—
Eli Lilly and Company	NKTR-358	—		1,200		1,259		3,700
Amgen, Inc.	Neulasta^®	1,250		1,250		2,500		2,500
Other		25		85		31		539
License, collaboration and other revenue		$	26,275	$	2,535	$	53,790	$	6,739

During the three and six months ended June 30, 2020, we recognized $42.1 million and $86.7 million, respectively, of revenue for performance obligations that we had satisfied in prior periods. This amount includes all of our royalty revenue and non-cash royalty revenue, as well as $25.0 million and $50.0 million in BMS Collaboration milestones, respectively, as further described below.

The following table presents the changes in our deferred revenue balance from our collaboration agreements during the six months ended June 30, 2020 (in thousands):


	Six Months Ended June 30, 2020
Deferred revenue—December 31, 2019	$	8,071
Recognition of previously unearned revenue	(3,790)
Deferred revenue—June 30, 2020	$	4,281

Our balance of deferred revenue contains the transaction price from our collaboration agreements allocated to performance obligations which are partially unsatisfied.

As of June 30, 2020, our collaboration agreements with partners included potential future payments for development and regulatory milestones totaling approximately $1.7 billion, including amounts from our agreements with BMS and Eli Lilly and Company described below. In addition, under our collaboration agreements we are entitled to receive contingent sales milestone payments, other contingent payments and royalty payments, as described below.

There have been no material changes to our collaboration agreements in the three and six months ended June 30, 2020, except as described below.

Bristol-Myers Squibb Company (BMS): Bempegaldesleukin, also referred to as NKTR-214

On February 13, 2018, we entered into a Strategic Collaboration Agreement (the BMS Collaboration Agreement) and a Share Purchase Agreement with BMS, both of which became effective on April 3, 2018. The agreement replaced the Clinical Trial Agreement we had entered into in September 2016. Pursuant to these current agreements, we and BMS are jointly developing bempegaldesleukin, including, without limitation, in combination with BMS’s Opdivo^® (nivolumab) and Opdivo^® plus Yervoy^® (ipilimumab), and other compounds of BMS, us or any third party. The parties have agreed to jointly commercialize

bempegaldesleukin on a worldwide basis. We retained the right to record all worldwide sales for bempegaldesleukin. We will share global commercialization profits and losses with BMS for bempegaldesleukin, with Nektar sharing 65% and BMS sharing 35% of the net profits and losses. The parties share the internal and external development costs for bempegaldesleukin in combination regimens based on each party’s relative ownership interest in the compounds included in the regimens. In accordance with the agreement, the parties share development costs for bempegaldesleukin in combination with Opdivo^®, 67.5% of costs to BMS and 32.5% to Nektar, and for bempegaldesleukin in a triplet combination with Opdivo^® and Yervoy^®78% of costs to BMS and 22% to Nektar. The parties share costs for the manufacturing of bempegaldesleukin, 35% of costs to BMS and 65% to Nektar.

Upon the effective date of the BMS Collaboration Agreement in April 2018, BMS paid us a non-refundable upfront cash payment of $1.0 billion. We are eligible to receive additional cash payments up to a total of approximately $1.455 billion (including the milestones from Amendment No. 1 described below) upon the achievement of certain development and regulatory milestones, of which we have received $25.0 million in March 2020 for the achievement of the first patient, first visit in the registrational muscle-invasive bladder cancer trial, and up to a total of $350.0 million upon the achievement of certain sales milestones. In April 2018, BMS also purchased 8,284,600 shares of our common stock pursuant to the Share Purchase Agreement for total additional cash consideration of $850.0 million.

On January 9, 2020, we and BMS entered into Amendment No. 1 (the Amendment) to the BMS Collaboration Agreement. Pursuant to the Amendment, we and BMS agreed to update the Collaboration Development Plan under which we are collaborating and developing bempegaldesleukin. The cost sharing under the Amendment remains unchanged. Additionally, we are eligible to receive an additional non-refundable, non-creditable milestone payment of $25.0 million following the achievement of the first patient, first visit in the registrational adjuvant melanoma trial, studying the combination of bempegaldesleukin and Opdivo^®. We are also eligible to receive non-refundable, creditable milestone payments of $25.0 million and $75.0 million following the achievement of the first patient, first visit in a registrational muscle-invasive bladder cancer trial and a registrational first-line non-small-cell lung cancer trial, respectively, in each case studying the combination of bempegaldesleukin and Opdivo^®. For the two creditable milestones, BMS is entitled to deduct the amounts paid pursuant to these milestones from future development milestones due to us under the original agreement. On January 30, 2020, the milestone for the first patient, first visit in the registrational muscle-invasive bladder cancer trial was achieved, and BMS paid us the $25.0 million milestone in March 2020. On July 27, 2020, the milestone for the first patient, first visit in the registrational adjuvant melanoma trial was achieved.

We determined that the BMS Collaboration Agreement falls within the scope of ASC 808, and we analogized to ASC 606 for the accounting for our performance obligation of the delivery of the licenses to develop and commercialize bempegaldesleukin.

During 2018, we aggregated the total consideration of $1.85 billion received under the agreements and allocated it between the stock purchase and the revenue-generating elements, because we and BMS negotiated the agreements together and the effective date of the BMS Collaboration Agreement was dependent upon the effective date of the Share Purchase Agreement. We recorded the estimated fair value of the shares of $790.2 million in stockholders’ equity. We allocated the remaining $1,059.8 million to the transaction price of the collaboration agreement, which we recognized in 2018. We consider the future potential development, regulatory and sales milestones of up to approximately $1.8 billion to be variable consideration.

During the three months ended March 31, 2020, we updated the transaction price by $25.0 million for the achievement of the first patient, first visit in the registrational muscle-invasive bladder cancer trial. During the three months ended June 30, 2020, we updated the transaction price by $25.0 million for the milestone for the first patient, first visit in the registrational adjuvant melanoma trial because we concluded that a reversal of the milestone was not probable. We achieved the first patient, first visit in the registrational adjuvant melanoma trial on July 27, 2020. Since we had already completed our sole performance obligation of delivery of the licenses, we recognized $25.0 million and $50.0 million in license, collaboration and other revenue during the three and six months ended June 30, 2020, respectively. We recognized the increase in the transaction price for the $25.0 million milestone for the first patient, first visit in the adjuvant melanoma trial as a contract asset, which we report within other current assets on our Condensed Consolidated Balance Sheet, since we had not achieved the triggering event as of June 30, 2020. We continue to exclude the other milestones from the transaction price as of June 30, 2020 due to the significant uncertainties involved with clinical development and regulatory approval. We re-evaluate the transaction price at each reporting period and as uncertain events are resolved or other changes in circumstances occur.

As mentioned above, BMS shares certain percentages of development costs incurred by us and we share certain percentages of development costs incurred by BMS. We consider these activities to represent collaborative activities under ASC 808, and we recognize such cost sharing proportionately with the performance of the underlying services. We recognize BMS’ reimbursement of our costs as a reduction of research and development expense and our reimbursement of BMS’ costs as research and development expense. During the three and six months ended June 30, 2020, we recorded $33.9 million and $65.1 million, respectively, as a reduction of research and development expense for BMS’ share of our expenses, net of our share of BMS’

expenses. During the three and six months ended June 30, 2019, we recorded $24.6 million and $53.4 million, respectively, as a reduction of research and development expense for BMS’ share of our expenses, net of our share of BMS’ expenses. As of June 30, 2020, we have recorded an unbilled receivable of $33.9 million from BMS in accounts receivable in our Condensed Consolidated Balance Sheet.

Eli Lilly and Company (Lilly): NKTR-358

On July 23, 2017, we entered into a worldwide license agreement with Eli Lilly and Company (Lilly), which became effective on August 23, 2017, to co-develop NKTR-358, a novel immunological drug candidate that we invented. Under the terms of the agreement, we (i) received an initial payment of $150.0 million in September 2017 and are eligible for up to $250.0 million in additional development milestones, (ii) will co-develop NKTR-358 with Lilly, for which we were responsible for completing Phase 1 clinical development and are responsible for certain drug product development and supply activities, (iii) will share with Lilly Phase 2 development costs with 75% of those costs borne by Lilly and 25% of the costs borne by us, (iv) will have the option to contribute funding to Phase 3 development on an indication-by-indication basis ranging from zero to 25% of development costs, and (v) will have the opportunity to receive up to double-digit sales royalty rates that escalate based upon our Phase 3 development cost contribution and the level of annual global product sales. Lilly will be responsible for all costs of global commercialization, and we will have an option to co-promote in the U.S. under certain conditions. A portion of the development milestones may be reduced by 50% under certain conditions, related to the final formulation of the approved product and the timing of prior approval (if any) of competitive products with a similar mechanism of action, which could reduce these milestone payments by 75% if both conditions occur.

The agreement will continue until Lilly no longer has any royalty payment obligations or, if earlier, the termination of the agreement in accordance with its terms. The agreement may be terminated by Lilly for convenience, and may also be terminated under certain other circumstances, including material breach.

We identified our license grant to Lilly, our ongoing Phase 1 clinical development obligation and our drug product development obligation as the significant performance obligations in the arrangement. The valuation of each performance obligation involves significant estimates and assumptions, including but not limited to, expected market opportunity and pricing, assumed royalty rates, clinical trial costs, timelines and likelihood of success; in each case these estimates and assumptions covering long time periods. We determined the selling price for the license based on a discounted cash flow analysis of projected revenues from NKTR-358 and development and commercial costs using a discount rate based on a market participant’s weighted-average cost of capital adjusted for forecasting risk. We determined the selling prices for our Phase 1 clinical development and drug product development deliverables based on the nature of the services to be performed and estimates of the associated efforts and third-party rates for similar services.

Although we are entitled to significant development milestones under this arrangement, through June 30, 2020, we have excluded such milestones from the transaction price due to the significant uncertainties involved with clinical development. We have therefore determined the transaction price to consist of the upfront payment of $150.0 million in September 2017. Based on our estimates of the standalone selling prices of the performance obligations, we allocated the $150.0 million upfront payment as $125.9 million to the license, $17.6 million to our portion of the Phase 1 clinical development and $6.5 million to the drug product development.

We recognized the $125.9 million of revenue allocated to the license upon the effective date of the license agreement in August 2017, since we determined that the license was a right to use our intellectual property, for which, as of the effective date, we had provided all necessary information to Lilly to benefit from the license and the license term had begun. We recognized revenue for our portion of the Phase 1 clinical development and drug product development using an input method, using costs incurred, as this method depicts our progress towards providing Lilly with the results of clinical trials and drug production processes. As of June 30, 2020, we completed our performance obligations and we have no deferred revenue related to this agreement.

Baxalta Inc. / Takeda Pharmaceutical Company Ltd: Hemophilia

We are a party to an exclusive research, development, license and manufacturing and supply agreement with Baxalta Inc. (Baxalta), a subsidiary of Takeda Pharmaceutical Company Ltd. (Takeda), entered into 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 for our active programs, which are now complete for Factor VIII, and are responsible for supplying Takeda with its requirements for our proprietary materials. Takeda 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^®, which was approved by the United States Food and Drug Administration (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., the European Union, and many other countries. As a result of the marketing authorization in the EU in January 2018, we earned a $10.0 million development milestone, which we received in March 2018. During 2018, we earned an additional $10.0 million milestone for annual sales of ADYNOVATE^®/ ADYNOVI™ reaching a certain specified amount. In addition, we are entitled to an additional sales milestone upon achievement of an annual worldwide net sales target and royalties based on worldwide net sales of products resulting from this agreement.

In October 2017, we entered into a right to sublicense agreement with Baxalta, under which we granted to Baxalta the right to grant a nonexclusive sublicense to certain patents that were previously exclusively licensed to Baxalta under our 2005 agreement. Under the right to sublicense agreement, Baxalta paid us $12.0 million in November 2017 and agreed to pay us single digit royalty payments based upon net sales of the products covered under the sublicense throughout the term of the agreement.

Our remaining unsatisfied performance obligation consists of our ongoing supply of PEGylation materials at a price less than the standalone selling price of these materials. As of June 30, 2020, our deferred revenue from this arrangement is not significant.

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 received a $50.0 million payment in the fourth quarter of 2010 in return for our guaranteeing the supply of certain quantities of our proprietary PEGylation materials to Amgen.

We determined that our obligation to manufacture and supply our PEGylation materials and to maintain the dedicated manufacturing suite solely for the production of such materials for Amgen represented an obligation to stand ready to manufacture such materials. We concluded that we should recognize revenue based on the passage of time as this method depicts the satisfaction of Amgen’s right to require production of PEGylation materials at any time. As of June 30, 2020, we have deferred revenue of approximately $1.7 million related to this agreement, which we expect to recognize through October 2020, the estimated end of our obligations under this agreement.

AstraZeneca AB: MOVANTIK^® (naloxegol oxalate), previously referred to as naloxegol and NKTR-118

In September 2009, we entered into 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^®. AstraZeneca is responsible for all research, development and commercialization costs and related decisions for MOVANTIK^®. In September 2014 and December 2014, MOVANTIK^® /MOVENTIG^® was approved in the US and EU, respectively. As of June 30, 2020, we have received a total of $385.0 million of upfront and contingent milestone payments from this agreement, all of which was received in or before 2015. 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^®.

In March 2016, AstraZeneca announced that it had entered into an agreement with ProStrakan Group plc, a subsidiary of Kyowa Hakko Kirin Co. Ltd. (Kirin), granting Kirin exclusive marketing rights to MOVENTIG^® in the EU, Iceland, Liechtenstein, Norway and Switzerland. Under our license agreement with AstraZeneca, we and AstraZeneca share the upfront payment, market access milestone payments, royalties and sales milestone payments made by Kirin to AstraZeneca with AstraZeneca receiving 60% and Nektar receiving 40%.

As of June 30, 2020, we do not have deferred revenue related to our agreement with AstraZeneca.

In April 2020, AstraZeneca announced that it had sublicensed its global commercialization rights for MOVANTIK^®, excluding Europe, Canada and Israel, to RedHill Biopharma. This sublicense does not change our rights under the agreement with AstraZeneca and our royalty rate, royalty term and future potential sales milestones remain unchanged.

Other

In addition, as of June 30, 2020, we have other collaboration agreements, including with our collaboration partner UCB Pharma, under which we are entitled to up to a total of $40.0 million of development milestone payments 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 and, therefore, have excluded all development milestones from the respective transaction prices for these agreements. As of June 30, 2020, we have deferred revenue of approximately $2.0 million related to these other collaboration agreements.

Organization and Summary of Significant Accounting Policies (Policies)	6 Months Ended
	Jun. 30, 2020
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Organization	Organization We are a research-based biopharmaceutical company headquartered in San Francisco, California and incorporated in Delaware. We are developing a pipeline of drug candidates that utilize our advanced polymer conjugate technology platforms, which are designed to enable the development of new molecular entities that target known mechanisms of action. Our research and development pipeline of new investigational drugs includes investigational treatments for cancer and autoimmune disease. 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.
Basis of Presentation and Principles of Consolidation	Basis of Presentation and Principles of Consolidation Our consolidated financial statements include the financial position, results of operations and cash flows of our wholly-owned subsidiaries: Inheris Biopharma, Inc. (Inheris), Nektar Therapeutics (India) Private Limited (Nektar India) and Nektar Therapeutics UK Limited. We have eliminated all intercompany accounts and transactions in consolidation. We prepared our Condensed Consolidated Financial Statements following the requirements of the Securities and Exchange Commission (SEC) for interim reporting. As permitted under those rules, we may condense or omit certain footnotes or other financial information that are normally required by U.S. generally accepted accounting principles (GAAP) for annual periods. In the opinion of management, these financial statements include all normal and recurring adjustments that we consider necessary for the fair presentation of our financial position and operating results. Our Condensed 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. We include translation gains and losses in accumulated other comprehensive income (loss) in the stockholders’ equity section of our Condensed Consolidated Balance Sheets. To date, such cumulative currency translation adjustments have not been significant to our consolidated financial position. Our comprehensive loss consists of our net loss plus our foreign currency translation gains and losses and unrealized holding gains and losses on available-for-sale securities. There were no significant reclassifications out of accumulated other comprehensive income (loss) to the statements of operations during the three and six months ended June 30, 2020 and 2019. The accompanying Condensed Consolidated Financial Statements are unaudited. The Condensed Consolidated Balance Sheet data as of December 31, 2019 was derived from the audited consolidated financial statements which are included in our Annual Report on Form 10-K for the year ended December 31, 2019 filed with the SEC on February 28, 2020. The information included in this Quarterly Report on Form 10-Q should be read in conjunction with the consolidated financial statements and the accompanying notes to those financial statements included in our Annual Report on Form 10-K for the year ended December 31, 2019. Revenue, expenses, assets, and liabilities can vary during each quarter of the year. The results and trends in these interim Condensed Consolidated Financial Statements are not necessarily indicative of the results to be expected for the full year or any other period.
Use of Estimates	Use of Estimates The preparation of consolidated financial statements in conformity with 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. The full extent to which the COVID-19 pandemic will directly or indirectly impact our business, results of operations and financial condition, including sales, expenses, reserves and allowances, manufacturing, clinical trials, research and development costs and employee-related amounts, will depend on future developments that are highly uncertain, including as a result of new information that may emerge concerning the COVID-19 pandemic and the actions taken to contain it or treat COVID-19, as well as the economic impact on local, regional, national and international customers and markets. We consider the effects of the COVID-19 pandemic in developing our estimates. Actual results could differ materially from those estimates and assumptions. As appropriate, we assess our estimates each period, update them to reflect current information and generally recognize any changes in such estimates in the period first identified.
Reclassifications	Reclassifications In December 2019, the FASB issued ASU 2019-12 - Income Taxes (Topic 740): Simplifying the Accounting for Income Taxes (ASU 2019-12). ASU 2019-12 created an exception to the incremental approach for intraperiod tax allocation when there is a loss from continuing operations and income or a gain from other items (for example, discontinued operations or other comprehensive income). Under the historical guidance, in this situation, an entity would record an income tax provision from other items, such as unrealized gains on available-for-sale securities reported in other comprehensive income, with an offsetting income tax benefit in continuing operations. Under ASU 2019-12, an entity would record no income tax provision. We elected to adopt ASU 2019-12 effective January 1, 2019 on a prospective basis in accordance with the guidance. Because we reported a net loss and unrealized gains on available-for-sale securities during 2019 and accordingly recorded a tax provision pursuant to the legacy guidance, we have recast such results from previously reported amounts. As a result, we eliminated the tax benefit in continuing operations and tax provision in other comprehensive income (loss), which totaled $0.4 million and $1.5 million for three and six months ended June 30, 2019. Additionally, 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.
Segment Information	Segment Information We operate in one business segment which focuses on applying our technology platform to develop novel drug candidates. 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.
Significant Concentrations	Significant Concentrations Our customers are primarily pharmaceutical and biotechnology companies that are located in the U.S. and Europe and with whom we have multi-year arrangements. Our accounts receivable balance contains billed and unbilled trade receivables from product sales, milestones (to the extent that they have been achieved and are due from the counterparty), other contingent payments and royalties, as well as reimbursable costs from collaborative research and development agreements. As of June 30, 2020, our accounts receivable includes $13.3 million under customer contracts from our collaboration partners and $33.9 million for unbilled net expense reimbursements from our collaboration partner Bristol-Myers Squibb Company (BMS). As of June 30, 2020, we also recorded a contract asset of $25.0 million, which we report in other current assets on our Condensed Consolidated Balance Sheet, from our collaboration partner BMS for the first patient, first visit for the registrational adjuvant melanoma trial (see Note 6 for additional information). As of December 31, 2019, our accounts receivable included $12.8 million from customer contracts and $24.0 million for unbilled net expense reimbursements from BMS. We generally do not require collateral from our customers. We perform a regular review of our customers’ credit risk and payment histories, including payments made after period end. Historically, we have not experienced credit losses from our accounts receivable. We have not recorded a reserve for credit losses at June 30, 2020 or December 31, 2019. We are dependent on our suppliers and contract manufacturers to provide raw materials and drugs 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. For our available-for-sale securities, we have significant concentrations of issuers in the banking and financial services, automotive and food and beverage industries. While our investment policy requires that we only invest in highly-rated securities and limit our exposure to any single issuer, the COVID-19 pandemic may materially affect the financial conditions of issuers. Additionally, pursuant to our investment policy, we may sell securities before maturity if the issuer’s credit rating has been downgraded below our minimum credit rating requirements, which may result in a loss on the sale. As a result of the COVID-19 pandemic, we have begun to see an increase in credit downgrades for certain of our securities. Accordingly, if the COVID-19 pandemic or other factors result in downgrades below our minimum credit rating requirements and if we decide to sell these securities, we may experience losses on such sales.
Collaborative Arrangements	Collaborative Arrangements We enter into collaboration arrangements with pharmaceutical and biotechnology collaboration partners, under which we may grant licenses to our collaboration partners to further develop and commercialize one of our proprietary drug candidates, either alone or in combination with the collaboration partners’ compounds, or grant licenses to partners to use our technology to research and develop their own proprietary drug candidates. We may also perform research, development, manufacturing and supply activities under our collaboration agreements. Consideration under these contracts may include an upfront payment, development and regulatory milestones and other contingent payments, expense reimbursements, royalties based on net sales of approved drugs, and commercial sales milestone payments. Additionally, these contracts may provide options for the customer to purchase our proprietary PEGylation materials, drug candidates or additional contract research and development services under separate contracts. When we enter into collaboration agreements, we assess whether the arrangements fall within the scope of ASC 808, Collaborative Arrangements (ASC 808) based on whether the arrangements involve joint operating activities and whether both parties have active participation in the arrangement and are exposed to significant risks and rewards of the arrangement. To the extent that the arrangement falls within the scope of ASC 808, we assess whether the payments between us and our collaboration partner fall within the scope of other accounting literature. If we conclude that payments from the collaboration partner to us represent consideration from a customer, such as license fees and contract research and development activities, we account for those payments within the scope of ASC 606, Revenue from Contracts with Customers (ASC 606). However, if we conclude that our collaboration partner is not a customer for certain activities and associated payments, such as for certain collaborative research, development, manufacturing and commercial activities, we present such payments as a reduction of research and development expense or general and administrative expense, based on where we present the underlying expense.
Revenue Recognition	Revenue Recognition For elements of those arrangements that we determine should be accounted for under ASC 606, we assess which activities in our collaboration agreements are performance obligations that should be accounted for separately and determine the transaction price of the arrangement, which includes the assessment of the probability of achievement of future milestones and other potential consideration. For arrangements that include multiple performance obligations, such as granting a license or performing contract research and development activities or participation on joint steering or other committees, we allocate upfront and milestone payments under a relative standalone selling price method. Accordingly, we develop assumptions that require judgment to determine the standalone selling price for each performance obligation identified in the contract. These key assumptions may include revenue forecasts, clinical development timelines and costs, discount rates and probabilities of clinical and regulatory success. Product Sales Product sales are primarily derived from manufacturing and supply agreements with our customers. We have assessed our current manufacturing and supply arrangements and have generally determined that they provide the customer an option to purchase our proprietary PEGylation materials. Accordingly, we treat each purchase order as a discrete exercise of the customer’s option (i.e. a separate contract) rather than as a component of the overall arrangement. The pricing for the manufacturing and supply is generally at a fixed price and may be subject to annual producer price index (PPI) adjustments. We invoice and recognize product sales when title and risk of loss pass to the customer, which generally occurs upon shipment. Customer payments are generally due 30 days from receipt of invoice. We test our products for adherence to technical specifications before shipment; accordingly, 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. For arrangements that include sales-based royalties, including commercial milestone payments based on the level of sales, we have concluded that the license is the predominant item to which the royalties relate. Accordingly, we recognize royalty revenue, including for our non-cash royalties, when the underlying sales occur based on our best estimates of sales of the drugs. Our partners generally pay royalties or commercial milestones after the end of the calendar quarter in accordance with contractual terms. We present commercial milestone payments within license, collaboration and other revenue. License, Collaboration and other Revenue License Grants: For collaboration arrangements that include a grant of a license to our intellectual property, we consider whether the license grant is distinct from the other performance obligations included in the arrangement. Generally, we would conclude that the license is distinct if the customer is able to benefit from the license with the resources available to it. For licenses that are distinct, we recognize revenues from nonrefundable, upfront payments and other consideration allocated to the license when the license term has begun and we have provided all necessary information regarding the underlying intellectual property to the customer, which generally occurs at or near the inception of the arrangement. Milestone Payments: At the inception of the arrangement and at each reporting date thereafter, we assess whether we should include any milestone payments or other forms of variable consideration in the transaction price, based on whether a significant reversal of revenue previously recognized is not probable upon resolution of the uncertainty. Since milestone payments may become payable to us upon the initiation of a clinical study, filing for or receipt of regulatory approval or the first commercial sale of a product, we review the relevant facts and circumstances to determine when we should update the transaction price, which may occur before the triggering event. When we do update the transaction price for milestone payments, we allocate it on a relative standalone selling price basis and record revenue on a cumulative catch-up basis, which results in recognizing revenue for previously satisfied performance obligations in such period. If we update the transaction price before the triggering event, we recognize the increase in the transaction price as a contract asset. Our partners generally pay development milestones subsequent to achievement of the triggering event. Research and Development Services: For amounts allocated to our research and development obligations in a collaboration arrangement, we recognize revenue over time using a proportional performance model, representing the transfer of goods or services as we perform activities over the term of the agreement.
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. Where we perform research and development activities under a joint development collaboration, such as our collaboration with BMS, we record the cost reimbursement from our partner as a reduction to research and development expense when reimbursement amounts are due to us under the agreement. We record an accrued expense 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 estimated activities performed by our third parties. We may also accrue expenses based on the total estimated cost of the treatment phase on a per patient basis and 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. We record an accrued expense for the estimated costs of our contract manufacturing 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 include upfront payments and milestone payments, which depend on factors such as the achievement of the completion of certain stages of the manufacturing process. For purposes of recognizing expense, we assess whether we consider the production process is sufficiently defined such that the resulting product can be considered the delivery of a good, as evidenced by predictive or contractually required yields in the production process or payment terms based on the actual yield, or the delivery of a service, where processes and yields are developing and less certain. If we consider the process to be the delivery of a good, we recognize expense when the drug product is delivered, or we otherwise bear risk of loss. If we consider the process to be the delivery of a service, we recognize expense based on our best estimates of the contract manufacturer’s progress towards completion of the stages in the contracts. We recognize and amortize upfront payments and accrue liabilities based on the specific terms of each arrangement. Certain arrangements may provide upfront payments for certain stages of the arrangement and milestone payments for the completion of certain stages, and, accordingly, we may record advance payments for services that have not been completed or goods not delivered and liabilities for stages where the contract manufacturer is entitled to a milestone payment. We capitalize advance payments for goods or services that will be used or rendered for future research and development activities and recognize expense as the related goods are delivered or services 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. We generally consider such increases or decreases in cost as changes in estimates and reflect them in research and development expenses in the period identified. Impairment of Assets and Other Costs for Terminated Program On January 14, 2020, the joint FDA Anesthetic Drug Products Advisory Committee and Drug Safety and Risk Management Committee did not recommend approval of our NDA for NKTR-181. As a result, we withdrew our NDA and decided to make no further investments in this program. On February 26, 2020, the Audit Committee of our Board of Directors approved management’s plan for the wind-down of Inheris and the NKTR-181 program. As a result, in the three months ended March 31, 2020, we wrote off $19.7 million of advance payments to contract manufacturers for commercial batches of NKTR-181. We also incurred $25.5 million of additional costs, primarily for non-cancellable commitments to our contract manufacturers and certain severance costs. We present these costs in the Impairment of assets and other costs for terminated program line in our Condensed Consolidated Statement of Operations. We did not incur any substantial costs related to the wind-down of Inheris and the NKTR-181 program in the three months ended June 30, 2020.
Income Taxes	Income Taxes For the three and six months ended June 30, 2020 and 2019, our income tax expense primarily results from taxable income in our Nektar India subsidiary. We have fully reserved our U.S. federal deferred tax assets generated from our net operating losses, as we believe it is not more likely than not that the benefit will be realized.
Recent Accounting Pronouncements	Recently Adopted Accounting Pronouncements On January 1, 2020, we adopted Accounting Standards Update 2018-18: Clarifying the Interaction between Topic 808 and Topic 606 (ASU 2018-18). The guidance clarifies that certain transactions between collaborative arrangement participants should be accounted for as revenue under ASC 606 when the collaborative arrangement participant is a customer for a promised good or service that is distinct within the collaborative arrangement. The guidance also precludes entities from presenting amounts related to transactions with a collaborative arrangement participant that is not a customer as revenue, unless those transactions are directly related to third-party sales. ASU 2018-18 is applied retrospectively to January 1, 2018, when we adopted ASC 606. Our adoption of ASU 2018-18 did not materially affect our revenue recognition. On January 1, 2020, we adopted ASU 2016-13: Financial Instruments - Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments. The guidance modifies the measurement and recognition of credit losses for most financial assets and certain other instruments. The amendment updates the guidance for measuring and recording credit losses on financial assets measured at amortized cost by replacing the “incurred loss” model with an “expected loss” model. As a result of adoption, we present these financial assets, which include our accounts receivable and available-for-sale debt securities, at the net amount we expect to collect. The amendment also requires that we record credit losses related to available-for-sale debt securities as an allowance through net income rather than reducing the carrying amount under the historical, other-than-temporary-impairment model. Our adoption of ASU 2016-13 did not materially affect our Condensed Consolidated Financial Statements.
Inventory	We value inventory at the lower of cost or net realizable value, and we write down defective or excess inventory to net realizable value based on historical experience or projected usage. We expense inventory related to our research and development activities as manufactured by us or when purchased.
Liability Related to Sale of Future Royalties	We periodically assess the estimated royalty payments to RPI from UCB and Roche, and, to the extent such payments are greater or less than our initial estimates or the timing of such payments is materially different from our original estimates, we will prospectively adjust the amortization of the Royalty Obligation.

Organization and Summary of Significant Accounting Policies - Additional Information (Detail)		3 Months Ended	6 Months Ended
	Apr. 13, 2020 USD ($)	Jun. 30, 2019 USD ($)	Jun. 30, 2020 USD ($) Segment	Jun. 30, 2019 USD ($)	Mar. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)	Oct. 05, 2015 USD ($)
Organization And Summary Of Significant Accounting Policies [Line Items]
Cash and investments in marketable securities			$ 1,210,563,000			$ 1,603,981,000
Accounting Standards Update [Extensible List]			us-gaap:AccountingStandardsUpdate201911Member
Tax provision on unrealized gain on available-for-sale securities, offset by benefit in continuing operations		$ 400,000		$ 1,500,000
Number of business segment \| Segment			1
Accounts receivable for expense reimbursements from collaboration partner			$ 47,245,000			36,802,000
Contract asset			25,000,000.0
Repayments of Senior Debt			250,000,000	$ 0
7.75% Senior Secured Notes Due October 2020 \| Senior Notes
Organization And Summary Of Significant Accounting Policies [Line Items]
Repayments of long term debt, including interest	$ 254,800,000
Debt instrument, face amount							$ 250,000,000.0
Senior secured notes, interest rate							7.75%
Repayments of Senior Debt	250,000,000.0
Cash paid for interest	$ 4,800,000
NKTR - 181
Organization And Summary Of Significant Accounting Policies [Line Items]
Write off of prepayment					$ 19,700,000
Purchase commitment, remaining minimum amount committed					$ 25,500,000
Collaboration Partner
Organization And Summary Of Significant Accounting Policies [Line Items]
Accounts receivable for expense reimbursements from collaboration partner			13,300,000			12,800,000
BMS Collaboration Agreement
Organization And Summary Of Significant Accounting Policies [Line Items]
Accounts receivable for expense reimbursements from collaboration partner			$ 33,900,000			$ 24,000,000.0

Cash and Investments in Marketable Securities - Portfolio of Cash and Investments in Marketable Securities (Detail) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities, available-for-sale, accumulated gross unrealized gain, before tax		$ 2,100
Debt securities, available-for-sale accumulated gross unrealized loss, before tax		(300)
Cash	$ 6,071	5,829
Total cash and investments in marketable securities	1,210,563	1,603,981
Fair Value Hierarchy Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities, available-for-sale, amortized cost	1,139,707
Debt securities, available-for-sale, accumulated gross unrealized gain, before tax	4,570
Debt securities, available-for-sale accumulated gross unrealized loss, before tax	(170)
Available-for-sale investments	1,144,107	1,507,655
Corporate notes and bonds \| Fair Value Hierarchy Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities, available-for-sale, amortized cost	893,901
Debt securities, available-for-sale, accumulated gross unrealized gain, before tax	4,095
Debt securities, available-for-sale accumulated gross unrealized loss, before tax	(143)
Available-for-sale investments	897,853	1,132,182
Corporate commercial paper \| Fair Value Hierarchy Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities, available-for-sale, amortized cost	235,811
Debt securities, available-for-sale, accumulated gross unrealized gain, before tax	475
Debt securities, available-for-sale accumulated gross unrealized loss, before tax	(26)
Available-for-sale investments	236,260	375,473
Obligations of U.S. government agencies \| Fair Value Hierarchy Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities, available-for-sale, amortized cost	9,995
Debt securities, available-for-sale, accumulated gross unrealized gain, before tax	0
Debt securities, available-for-sale accumulated gross unrealized loss, before tax	(1)
Available-for-sale investments	9,994	0
Money Market Funds \| Fair Value Hierarchy Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments in marketable securities	52,135	83,546
Certificates of Deposit
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments in marketable securities	$ 8,250	$ 6,951

License and Collaboration Agreements - Additional Information (Detail) - USD ($)			1 Months Ended							3 Months Ended				6 Months Ended		12 Months Ended	76 Months Ended
	Feb. 13, 2018	Aug. 23, 2017	Mar. 31, 2020	Apr. 30, 2018	Jan. 31, 2018	Nov. 30, 2017	Sep. 30, 2017	Aug. 31, 2017	Mar. 31, 2016	Jun. 30, 2020	Mar. 31, 2020	Jun. 30, 2019	Dec. 31, 2010	Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2018	Dec. 31, 2015	Jan. 09, 2020	Dec. 31, 2019
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Revenue recognized in period related to performance in prior periods										$ 42,100,000				$ 86,700,000
Potential future additional development and regulatory milestones										1,700,000,000				1,700,000,000
Accounts receivable										47,245,000				47,245,000					$ 36,802,000
Revenue, excluding assessed tax										48,847,000		$ 23,315,000		99,420,000	$ 51,537,000
Deferred revenue										4,281,000				4,281,000					$ 8,071,000
BMS Collaboration Agreement
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Sales milestone, revenue			$ 25,000,000.0							25,000,000.0				50,000,000.0
BMS Collaboration Agreement \| Bempegaldesleukin \| Nektar's
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Global commercialization profits and losses sharing percentage	65.00%
Percentage of sharing production costs	65.00%
Upfront and milestone payments received from license agreements				$ 1,000,000,000.0
Maximum total additional cash payments receivable upon achievement of certain development and regulatory milestones														1,455,000,000
BMS Collaboration Agreement \| Bempegaldesleukin \| Nektar's \| Milestone One
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Potential future additional payments for development milestones																		$ 25,000,000.0
BMS Collaboration Agreement \| Bempegaldesleukin \| Nektar's \| Milestone Two
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Potential future additional payments for development milestones																		25,000,000.0
BMS Collaboration Agreement \| Bempegaldesleukin \| Nektar's \| Milestone Three
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Potential future additional payments for development milestones																		$ 75,000,000.0
BMS Collaboration Agreement \| Bempegaldesleukin \| Nektar's \| Maximum
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Eligible additional cash payments receivable upon achievement of certain sales milestones				$ 350,000,000.0
BMS Collaboration Agreement \| Bempegaldesleukin \| Nektar's \| Opdivo
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Percentage of sharing development costs	32.50%
BMS Collaboration Agreement \| Bempegaldesleukin \| Nektar's \| Opdivo and Yervoy
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Percentage of sharing development costs	22.00%
NKTR-358 \| Nektar's
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Received upfront and milestone payment							$ 150,000,000.0
Percentage of sharing in Phase 2 development costs		25.00%
Nektar
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Percentage of upfront payment, market access milestones, royalties and sales milestones									40.00%
Bristol-Myers Squibb Company \| Purchase Agreement
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Shares issued (in shares)				8,284,600
Sale of stock consideration received				$ 850,000,000.0
Bristol-Myers Squibb Company \| Bempegaldesleukin \| Research and Development Expense
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Reimbursement of expenses										33,900,000		$ 24,600,000		65,100,000	$ 53,400,000
Bristol-Myers Squibb Company \| BMS Collaboration Agreement \| Purchase Agreement
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Total consideration received under agreements																$ 1,850,000,000
Estimated fair value of shares																790,200,000
Remaining amount allocated to transaction price										25,000,000.0	$ 25,000,000.0			50,000,000.0		1,059,800,000
Potential future development, regulatory and sales milestones																1,800,000,000
Bristol-Myers Squibb Company \| BMS Collaboration Agreement \| Bempegaldesleukin
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Global commercialization profits and losses sharing percentage	35.00%
Percentage of sharing production costs	35.00%
Bristol-Myers Squibb Company \| BMS Collaboration Agreement \| Bempegaldesleukin \| Opdivo
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Percentage of sharing development costs	67.50%
Bristol-Myers Squibb Company \| BMS Collaboration Agreement \| Bempegaldesleukin \| Opdivo and Yervoy
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Percentage of sharing development costs	78.00%
Eli Lilly and Company \| NKTR-358 \| ASC 606
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Revenue, excluding assessed tax								$ 125,900,000
Eli Lilly and Company \| NKTR-358 License
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Amount of transaction price allocated to performance obligation							125,900,000
Eli Lilly and Company \| NKTR-358 \| Maximum
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Potential future additional development and regulatory milestones		$ 250,000,000.0
Eli Lilly and Company \| NKTR-358 \| Nektar's
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Percentage of regulatory milestones payments will be reduced under certain conditions		50.00%
Percentage of regulatory milestones payments will be reduced if conditions occur		75.00%
Eli Lilly and Company \| NKTR-358 \| Nektar's \| Maximum
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Percentage of funding phase 3 development costs on an indication by indication basis borne		25.00%
Eli Lilly and Company \| NKTR-358 \| Nektar's \| Minimum
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Percentage of funding phase 3 development costs on an indication by indication basis borne		0.00%
Eli Lilly and Company \| Phase 1 Clinical Development \| NKTR-358 License
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Amount of transaction price allocated to performance obligation							17,600,000
Eli Lilly and Company \| Drug Product Development \| NKTR-358 License
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Amount of transaction price allocated to performance obligation							$ 6,500,000
Eli Lilly \| NKTR-358
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Percentage of sharing in Phase 2 development costs		75.00%
Baxalta Incorporated/Takeda \| Hemophilia
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Received under right to sublicense agreement						$ 12,000,000.0
Baxalta Incorporated/Takeda \| Hemophilia \| Annual Sales Level Milestone
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Revenue, excluding assessed tax																$ 10,000,000.0
Baxalta Incorporated/Takeda \| Hemophilia \| European Union
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Revenue, excluding assessed tax					$ 10,000,000.0
Amgen, Inc.
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Received upfront and milestone payment													$ 50,000,000.0
Amgen, Inc. \| ASC 606
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Deferred revenue										1,700,000				1,700,000
AstraZeneca AB \| MOVANTIK and MOVENTIG
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Received upfront and milestone payment																	$ 385,000,000.0
AstraZeneca AB \| AstraZeneca-Kirin
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Deferred revenue										0				0
Percentage of upfront payment, market access milestone payments, royalties and sales milestone payments from sublicense agreement retained by our collaboration partner									60.00%
Other
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Potential future additional payments for development milestones										40,000,000.0				40,000,000.0
Deferred revenue										$ 2,000,000.0				$ 2,000,000.0

Liability Related to Sale of Future Royalties	6 Months Ended
Liability Related to Sale of Future Royalties	Jun. 30, 2020
Other Liabilities Disclosure [Abstract]
Liability Related to Sale of Future Royalties	Liability Related to 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 are 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 continue to account for these royalties as revenue. We recorded the $124.0 million in proceeds from this transaction as a liability (Royalty Obligation) that is amortized using the interest method over the estimated life of the Purchase and Sale Agreement as royalties from the CIMZIA^® and MIRCERA^® products are remitted directly to RPI. During the six months ended June 30, 2020 and 2019, we recognized $17.6 million and $17.3 million, respectively, in non-cash royalty revenue from net sales of CIMZIA^® and MIRCERA^®, and we recorded $13.7 million and $12.0 million, respectively, of related non-cash interest expense. We periodically assess the estimated royalty payments to RPI from UCB and Roche, and, to the extent such payments are greater or less than our initial estimates or the timing of such payments is materially different from our original estimates, we will prospectively adjust the amortization of the Royalty Obligation. From inception through 2017, our estimate of the total interest expense on the Royalty Obligation resulted in an effective annual interest rate of approximately 17%. During the three months ended December 31, 2017, our estimate of the effective annual interest rate over the life of the agreement increased to 17.6%, which resulted in a prospective interest rate of approximately 21%. During the three months ended December 31, 2018, primarily as a result of increases in the forecasted sales of MIRCERA^®, our estimate of the effective annual interest rate over the life of the agreement increased to 18.7%, which results in a prospective interest rate of 29%. During the three month period ended December 31, 2019, primarily as a result of increases in the forecasted sales of CIMZIA^® and MIRCERA^®, our estimate of the effective annual interest rate over the life of the agreement increased to 19.5%, which results in a prospective interest rate of 38%. This rate remains unchanged for the three and six months ended June 30, 2020. 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 (often with time limitations) that are customary for a transaction of this nature. For example, we provided representations and warranties concerning intellectual property matters in the Purchase and Sale Agreement; however, the time limitation we have to indemnify RPI with respect to any breach of these intellectual property-based representations and warranties has passed. 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	6 Months Ended
Commitments and Contingencies	Jun. 30, 2020
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	Commitments and Contingencies 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 October 30, 2018, we and certain of our executives were named in a putative securities class action complaint filed in the U.S. District Court for the Northern District of California (U.S. District Court in California), which complaint was subsequently amended on May 15, 2019. Also, on February 13, 2019, and February 18, 2019, shareholder derivative complaints were filed in the U.S. District Court for the District of Delaware naming the CEO, CFO and certain members of Nektar’s board. These class action and shareholder derivative actions assert, among other things, that for a period beginning at least from November 11, 2017 through October 2, 2018, our stock was inflated due to alleged misrepresentations about the efficacy and safety of bempegaldesleukin. On July 13, 2020, the U.S. District Court in California Court granted Nektar’s motion to dismiss all claims in this securities class action filing, stating (among other things) that the amended complaint failed “to adequately allege that any of the statements … identified by Plaintiffs were false or misleading.” The plaintiffs in this matter have 28 days from July 13, 2020, to file another amended complaint. In addition, on August 19, 2019, we and certain of our executives were named in a putative securities class action complaint filed in U.S. District Court in California, which complaint was subsequently amended on January 24, 2020. Also, on February 11, 2020, and on February 20, 2020, shareholder derivative complaints were filed in U.S. District Court in California naming the CEO, CFO and certain members of Nektar’s board, which derivative complaints were consolidated and subsequently amended on July 1, 2020. The class action and shareholder derivative complaints assert, among other things, that for a period between February 15, 2019 and August 8, 2019, inclusive, our stock was inflated due to an alleged failure to disclose a reduction in the planned number of bempegaldesleukin clinical trials and a bempegaldesleukin manufacturing issue. All of the securities class action lawsuits and derivative complaints are in the early stages. Accordingly, we cannot reasonably estimate a potential future loss or a range of potential future losses. However, an unfavorable resolution could potentially have a material adverse effect on our business, financial condition, and results of operations or prospects, and potentially result in paying monetary damages. We have recorded no liability for these matters in our Condensed Consolidated Balance Sheets at either June 30, 2020 or December 31, 2019. 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 and PEGylation materials 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. The term of these indemnification obligations is generally perpetual any time after execution of the agreement. There is generally no limitation on the potential amount of future payments we could be required to make under these indemnification obligations. From time to time, we enter into other strategic agreements such as divestitures and financing transactions pursuant to which we are required to make representations and warranties and undertake to perform or comply with certain covenants, including our obligation to RPI described in Note 4. In the event it is determined that we breached certain of the representations and warranties or covenants made by us in any such agreements, we could incur substantial indemnification liabilities depending on the timing, nature, and amount of any such claims. To date, we have not incurred costs to defend lawsuits or settle claims related to these indemnification obligations, representations or warranties. Because the aggregate amount of any potential indemnification obligation is not a stated amount, we cannot reasonably estimate the overall maximum amount of any such obligations. We have recorded no liabilities for these obligations in our Condensed Consolidated Balance Sheets at either June 30, 2020 or December 31, 2019.

Cash and Investments in Marketable Securities - Additional Information (Detail) - USD ($)	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2019
Cash and Investments in Marketable Securities [Line Items]
Maximum maturity term for debt securities investment			2 years
Weighted average maturity term for debt securities investment (or less)			1 year
Available-for-sale securities, sold	$ 41,700,000	$ 0	$ 41,700,000	$ 0
Accrued interest receivable	$ 6,100,000		$ 6,100,000		$ 6,500,000
Minimum
Cash and Investments in Marketable Securities [Line Items]
Long term investment maturity period			1 year		1 year
Maximum
Cash and Investments in Marketable Securities [Line Items]
Long term investment maturity period			2 years		2 years

Inventory (Details) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Inventory Disclosure [Abstract]
Raw materials	$ 1,681	$ 1,673
Work-in-process	8,555	8,267
Finished goods	2,348	2,725
Total inventory	$ 12,584	$ 12,665

Liability Related to Sale of Future Royalties - Additional Information (Detail) - USD ($) $ in Thousands		3 Months Ended					6 Months Ended		70 Months Ended
	Feb. 24, 2012	Jun. 30, 2020	Dec. 31, 2019	Jun. 30, 2019	Dec. 31, 2018	Dec. 31, 2017	Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2017
Liability Related to Sale of Future Royalties [Line Items]
Non-cash royalty revenue related to sale of future royalties							$ (17,579)	$ (17,321)
Non-cash interest expense on liability related to sale of future royalties		$ (6,691)		$ (5,975)			$ (13,659)	$ (12,040)
Annual interest rate			19.50%		18.70%	17.60%			17.00%
Prospective interest rate			38.00%		29.00%	21.00%
Purchase and Sale Agreement with RPI
Liability Related to 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

Condensed Consolidated Balance Sheets (Unaudited) (Parenthetical) - $ / shares	Jun. 30, 2020	Dec. 31, 2019
Statement of Financial Position [Abstract]
Preferred stock, par value (in dollars per share)	$ 0.0001	$ 0.0001
Preferred stock, shares authorized (in shares)	10,000,000	10,000,000
Preferred stock, shares designated (in shares)	0	0
Preferred stock, shares outstanding (in shares)	0	0
Common stock, par value (in dollars per share)	$ 0.0001	$ 0.0001
Common stock, shares authorized (in shares)	300,000,000	300,000,000
Common stock, shares outstanding (in shares)	178,810,000	176,505,000

Cash and Investments in Marketable Securities - Cash and Investments in Marketable Securities, Including Cash Equivalents (Detail) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Cash and cash equivalents	$ 58,206	$ 96,363
Short-term investments	980,191	1,228,499
Long-term investments	172,166	279,119
Total cash and investments in marketable securities	$ 1,210,563	$ 1,603,981

Commitments and Contingencies - Additional Information (Detail) - USD ($)	Jun. 30, 2020	Dec. 31, 2019
Indemnification Obligation
Loss Contingencies [Line Items]
Litigation matters, liabilities	$ 0	$ 0

License and Collaboration Agreements - Changes in Deferred Revenue Balance from Collaboration Agreements (Detail) $ in Thousands	6 Months Ended
	Jun. 30, 2020 USD ($)
Contract With Customer, Liability [Roll Forward]
Deferred revenue, Beginning balance	$ 8,071
Recognition of previously unearned revenue	(3,790)
Deferred revenue, Ending balance	$ 4,281

Stock-Based Compensation - Activity (Detail) - $ / shares		3 Months Ended		6 Months Ended
	Jun. 17, 2020	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares issued under equity compensation plans (in shares)		0	95,000	49,000	115,000
Performance Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock, additional shares authorized (in shares)	10,000,000
Employee Stock Purchase Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock, additional shares authorized (in shares)	1,000,000
Stock Options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted stock options (in shares)		0	17.00	11.88	18.51
Weighted average grant-date fair value, options (in dollars per share)		$ 275,000	$ 263,000	$ 520,000	$ 396,000
Restricted Stock Units (RSU)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Awards granted (in shares)		21.65	31.76	20.36	34.85
Weighted average grant-date fair value, RSUs (in dollars per share)		$ 947,000	$ 738,000	$ 2,305,000	$ 1,436,000