Ironwood Pharmaceuticals (IRWD) 10-K 17 Feb 21 2020 FY Annual report Financial data

Document and Entity Information

Document and Entity Information - USD ($)	12 Months Ended
	Dec. 31, 2020	Feb. 10, 2021	Jun. 30, 2020
Cover [Abstract]
Document Type	10-K
Document Annual Report	true
Document Period End Date	Dec. 31, 2020
Document Transition Report	false
Entity File Number	001-34620
Entity Registrant Name	IRONWOOD PHARMACEUTICALS, INC.
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	04-3404176
Entity Address, Address Line One	100 Summer Street
Entity Address, Address Line Two	Suite 2300
Entity Address, City or Town	Boston
Entity Address, State or Province	MA
Entity Address, Postal Zip Code	02110
City Area Code	617
Local Phone Number	621-7722
Title of 12(b) Security	Class A Common Stock, $0.001 par value
Entity Listing, Par Value Per Share	$ 0.001
Trading Symbol	IRWD
Security Exchange Name	NASDAQ
Entity Well-known Seasoned Issuer	Yes
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
ICFR Auditor Attestation Flag	true
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Public Float			$ 1,634,804,172
Entity Common Stock, Shares Outstanding		160,962,175
Entity Central Index Key	0001446847
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2020
Document Fiscal Period Focus	FY
Amendment Flag	false

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Current assets:
Cash and cash equivalents	$ 362,564	$ 177,023
Accounts receivable, net	122,351	11,279
Related party accounts receivable, net		105,967
Inventory, net		648
Prepaid expenses and other current assets	9,189	10,685
Restricted cash	1,735	1,250
Total current assets	495,839	306,852
Restricted cash, net of current portion	485	971
Accounts receivable, net of current portion	23,401	32,597
Property and equipment, net	8,929	12,429
Operating lease right-of-use assets	16,576	17,743
Convertible note hedges	13,065	31,366
Other assets	943	790
Total assets	559,238	402,748
Current liabilities:
Accounts payable	661	3,978
Related party accounts payable, net		1,509
Accrued research and development costs	1,898	2,956
Accrued expenses and other current liabilities	26,486	30,465
Current portion of operating lease liabilities	3,128	1,146
Deferred revenue		875
Total current liabilities	32,173	40,929
Note hedge warrants	12,088	24,260
Convertible senior notes	430,256	407,994
Operating lease obligations, net of current portion	20,318	22,082
Other liabilities	1,763	734
Commitments and contingencies
Stockholders' equity (deficit):
Preferred stock, $0.001 par value, 75,000,000 shares authorized, no shares issued and outstanding
Class A Common Stock, $0.001 par value, 500,000,000 shares authorized and 160,616,675 issued and outstanding at December 31, 2020 and 500,000,000 shares authorized and 157,535,962 shares issued and outstanding at December 31, 2019	161	158
Additional paid-in capital	1,528,535	1,478,823
Accumulated deficit	(1,466,056)	(1,572,232)
Total stockholders' equity (deficit)	62,640	(93,251)
Total liabilities and stockholders' equity (deficit)	$ 559,238	$ 402,748

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) - $ / shares	Dec. 31, 2020	Dec. 31, 2019
Preferred stock
Preferred stock, par value (in dollars per share)	$ 0.001	$ 0.001
Preferred stock, shares authorized	75,000,000	75,000,000
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0
Common stock
Common stock, par value (in dollars per share)	$ 0.001	$ 0.001
Common stock, shares authorized	500,000,000	500,000,000
Common stock, shares issued	160,616,675	157,535,962
Common stock, shares outstanding	160,616,675	157,535,962

Consolidated Statements of Oper

Consolidated Statements of Operations - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Revenues:
Total revenues	$ 389,523	$ 428,413	$ 346,639
Cost and expenses:
Cost of revenues, excluding amortization of acquired intangible assets	3,136	23,875	32,751
Write-down of commercial supply and inventory to net realizable value and (settlement) loss on non-cancellable purchase commitments		(3,530)	247
Research and development	88,062	115,044	101,060
Selling, general and administrative	140,003	172,450	219,676
Amortization of acquired intangible assets			8,111
Gain on fair value remeasurement of contingent consideration			(31,045)
Gain on lease modification		(3,169)
Restructuring expenses	15,382	3,620	14,715
Impairment of intangible assets			151,794
Total cost and expenses	246,583	308,290	497,309
Income (loss) from operations	142,940	120,123	(150,670)
Other (expense) income:
Interest expense	(29,478)	(36,602)	(37,724)
Interest and investment income	1,504	2,862	2,991
Gain (loss) on derivatives	(6,129)	3,023	(8,743)
Loss on extinguishment of debt		(30,977)
Other income	24	514
Other expense, net	(34,079)	(61,180)	(43,476)
Income (loss) from continuing operations, before income taxes	108,861	58,943	(194,146)
Income tax expense	2,685	0	0
Income (loss) from continuing operations	106,176	58,943	(194,146)
Loss from discontinued operations, net of income taxes		(37,438)	(88,222)
Net income (loss)	106,176	21,505	(282,368)
Comprehensive income (loss)	$ 106,176	$ 21,505	$ (282,289)
Income (loss) per share from continuing operations, net of income taxes - basic (in dollars per share)	$ 0.67	$ 0.38	$ (1.27)
Income (loss) per share from continuing operations, net of income taxes - diluted (in dollars per share)	0.66	0.38	(1.27)
Loss per share from discontinued operations, net of income taxes - basic and diluted (in dollars per share)		(0.24)	(0.58)
Net income (loss) per share - basic (in dollars per share)	0.67	0.14	(1.85)
Net income (loss) per share - diluted (in dollars per share)	$ 0.66	$ 0.14	$ (1.85)
Weighted average shares used in computing net income per share - basic: (in shares)	159,427	156,023	152,634
Weighted average shares used in computing net income per share - diluted: (in shares)	160,655	156,023	152,634
Collaborative arrangements revenue
Revenues:
Total revenues	$ 381,545	$ 379,652	$ 272,839
Product revenue, net
Revenues:
Total revenues			3,445
Sale of active pharmaceutical ingredient
Revenues:
Total revenues	$ 7,978	$ 48,761	$ 70,355

Consolidated Statements of Comp

Consolidated Statements of Comprehensive Income (Loss) $ in Thousands	12 Months Ended
	Dec. 31, 2018USD ($)
Condensed Consolidated Statements of Comprehensive Income (Loss)
Net income (loss)	$ (282,368)
Other comprehensive income:
Unrealized gains on available-for-sale securities	79
Total other comprehensive income	79
Comprehensive income (loss)	$ (282,289)

Consolidated Statements of Stoc

Consolidated Statements of Stockholders' Equity (Deficit) - USD ($) $ in Thousands	Class A common stockCommon Stock	Class B common stockCommon Stock	Additional paid-in capital	Accumulated deficit	Accumulated other comprehensive income (loss)	Total
Balance at Dec. 31, 2017	$ 137	$ 14	$ 1,318,536	$ (1,308,760)	$ (79)	$ 9,848
Balance (in shares) at Dec. 31, 2017	136,465,526	13,983,762
Increase (Decrease) in Stockholders' Equity
Issuance of common stock related to share-based awards and employee stock purchase plan	$ 3		32,058			32,061
Issuance of common stock related to share-based awards and employee stock purchase plan (in shares)	3,201,042	764,361
Issuance of common stock upon exercise of stock options and employee stock purchase plan, net of cancellations	$ 4		13,597			13,601
Issuance of common stock upon exercise of stock options and employee stock purchase plan, net of cancellations (in shares)	3,121,271
Conversion of Class B common stock to Class A common stock	$ 14	$ (14)
Conversion of Class B common stock to Class A common stock (in shares)	14,748,123	(14,748,123)
Share-based compensation expense related to share-based awards and employee stock purchase plan			44,009			44,009
Unrealized gains (losses) on available-for-sale securities					$ 79	79
Net income (loss)				(282,368)		(282,368)
Balance at Dec. 31, 2018	$ 154		1,394,603	(1,591,128)		(196,371)
Balance (in shares) at Dec. 31, 2018	154,414,691
Increase (Decrease) in Stockholders' Equity
Share-based compensation expense related to share-based awards and employee stock purchase plan			32,331			32,331
Equity component of convertible senior notes			92,502			92,502
Equity component of issuance costs for convertible senior notes			(2,092)			(2,092)
Purchase of capped calls			(25,159)			(25,159)
Equity component of the partial repurchase of the 2022 Convertible Notes			(26,959)			(26,959)
Dividend of sGC business				(2,609)		(2,609)
Net income (loss)				21,505		21,505
Balance at Dec. 31, 2019	$ 158		1,478,823	(1,572,232)		$ (93,251)
Balance (in shares) at Dec. 31, 2019	157,535,962					157,535,962
Increase (Decrease) in Stockholders' Equity
Issuance of common stock upon exercise of stock options and employee stock purchase plan	$ 3		18,537			$ 18,540
Issuance of common stock upon exercise of stock options and employee stock purchase plan (in shares)	3,080,713
Share-based compensation expense related to share-based awards and employee stock purchase plan			31,175			31,175
Net income (loss)				106,176		106,176
Balance at Dec. 31, 2020	$ 161		$ 1,528,535	$ (1,466,056)		$ 62,640
Balance (in shares) at Dec. 31, 2020	160,616,675					160,616,675

Consolidated Statements of Cash

Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Cash flows from operating activities:
Net income (loss)	$ 106,176	$ 21,505	$ (282,368)
Adjustments to reconcile net income (loss) to net cash used in operating activities:
Depreciation and amortization	3,564	5,580	3,859
Amortization of acquired intangible assets			8,111
Impairment of intangible assets			151,794
Loss on disposal of property and equipment	470	146	(1,867)
Share-based compensation expense	31,175	31,278	40,526
Gain on lease modification		(3,169)
Change in fair value of note hedge warrants	(12,172)	16,232	(58,425)
Change in fair value of convertible note hedges	18,301	(19,255)	67,168
Write-down of commercial supply and inventory to net realizable value and settlement loss on non-cancellable purchase commitments		(3,530)	219
Write-down of excess non-cancellable ZURAMPIC and DUZALLO sample purchase commitments			390
Accretion of discount/premium on investment securities			(165)
Loss on extinguishment of debt		30,977
Non-cash interest expense	22,263	19,590	17,601
Non-cash change in fair value of contingent consideration			(31,045)
Changes in assets and liabilities:
Accounts receivable and related party accounts receivable, net	4,091	(68,893)	1,207
Inventory, net	648		(806)
Prepaid expenses and other current assets	1,515	(1,046)	(3,727)
Other assets	(153)	159	702
Accounts payable, related party accounts payable and accrued expenses	(7,523)	(32,700)	2,678
Accrued research and development costs	(1,058)	(483)	542
Operating lease right-of-use assets	1,167	14,141
Operating lease liabilities	218	(12,046)
Deferred revenue	(875)	875
Deferred rent			916
Other liabilities	1,029
Net cash provided by (used in) continuing operating activities	168,836	(639)	(82,690)
Net cash provided by discontinued operating activities		11,364	11,808
Net cash provided by (used in) operating activities	168,836	10,725	(70,882)
Cash flows from investing activities:
Purchases of available-for-sale securities			(3,241)
Sales and maturities of available-for-sale securities			99,165
Purchases of property and equipment	(1,842)	(7,189)	(351)
Proceeds from sale of property and equipment		268	1,563
Net cash used in continuing investing activities	(1,842)	(6,921)	97,136
Net cash used in discontinued investing activities		(4,223)	(8,270)
Net cash used in investing activities	(1,842)	(11,144)	88,866
Cash flows from financing activities:
Proceeds from issuance of convertible senior notes		400,000
Purchase of capped calls		(25,159)
Proceeds from partial termination of convertible note hedges and note hedge warrants		3,174
Costs associated with issuance of convertible senior notes		(9,048)
Proceeds from exercise of stock options and employee stock purchase plan	18,546	13,595	32,061
Payments on capital lease obligations			(1,824)
Payments for partial repurchase of 2022 Convertible Notes		(227,338)
Payments on 8.375% Notes due 2026		(156,409)
Payments on contingent purchase price consideration			(165)
Net cash provided by (used in) continuing financing activities	18,546	(1,185)	30,072
Net cash provided by (used in) financing activities	18,546	(1,185)	30,072
Net increase (decrease) in cash, cash equivalents and restricted cash	185,540	(1,604)	48,056
Cash, cash equivalents and restricted cash, beginning of period	179,244	180,848	132,792
Cash, cash equivalents and restricted cash, end of period	364,784	179,244	180,848
Supplemental cash flow disclosure:
Cash paid for interest	7,216	17,584	18,235
Cash paid for income taxes	1,848
Non-cash investing and financing activities
Purchases under capital leases			664
Extinguishment of capital leases			2,687
Recognition of asset retirement obligation		486
Fixed asset purchases in accounts payable and accrued expenses		$ 1,282	$ 439
Cash paid for income taxes	$ 1,848

Consolidated Statements of Ca_2

Consolidated Statements of Cash Flows (Parenthetical) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Reconciliation of cash, cash equivalents, and restricted cash to the condensed consolidated balance sheets
Cash and cash equivalents	$ 362,564	$ 177,023	$ 173,172
Restricted cash	2,220	2,221	7,676
Total cash, cash equivalents, and restricted cash	$ 364,784	$ 179,244	$ 180,848	$ 132,792

Nature of Business

Nature of Business	12 Months Ended
	Dec. 31, 2020
Disclosure Text Block
Nature of Business	1. Nature of Business ​ Ironwood Pharmaceuticals, Inc. (“Ironwood” or the “Company”) is a gastrointestinal (“GI”) healthcare company dedicated to advancing the treatment of GI diseases and redefining the standard of care for GI patients. The Company is focused on the development and commercialization of innovative GI product opportunities in areas of significant unmet need, leveraging its demonstrated expertise and capabilities in GI diseases. ​ LINZESS ® ® ​ The Company has strategic partnerships with leading pharmaceutical companies to support the development and commercialization of linaclotide throughout the world. The Company and its partner, AbbVie Inc. (together with its affiliates, “AbbVie”) (successor to Allergan plc (together with its affiliates), “Allergan”), began commercializing LINZESS in the U.S. in December 2012. Under the Company’s collaboration with AbbVie for North America, total net sales of LINZESS in the U.S., as recorded by AbbVie, are reduced by commercial costs incurred by each party, and the resulting amount is shared equally between the Company and AbbVie. AbbVie also has an exclusive license from the Company to develop and commercialize linaclotide in all countries other than China (including Hong Kong and Macau), Japan and the countries and territories of North America (the “AbbVie License Territory”). On a country-by-country and product-by-product basis in the AbbVie License Territory, AbbVie pays the Company a royalty as a percentage of net sales of products containing linaclotide as an active ingredient. In addition, AbbVie has exclusive rights to commercialize linaclotide in Canada as CONSTELLA and in Mexico as LINZESS. ​ Astellas Pharma Inc. (“Astellas”), the Company’s partner in Japan, has an exclusive license to develop and commercialize linaclotide in Japan. In March 2017, Astellas began commercializing LINZESS for the treatment of adults with IBS-C in Japan, and in September 2018, Astellas began commercializing LINZESS for the treatment of adults with chronic constipation in Japan. In August 2019, the Company amended and restated its license agreement with Astellas. Effective in 2020, Company is no longer responsible for the supply of linaclotide active pharmaceutical ingredient (“API”) to Astellas (Note 6). ​ In October 2012, the Company and AstraZeneca AB (together with its affiliates) (“AstraZeneca”) entered into a collaboration agreement to co-develop and co-commercialize linaclotide in China (including Hong Kong and Macau) (the “AstraZeneca License Territory”). In September 2019, the Company amended and restated its existing collaboration agreement with AstraZeneca whereby AstraZeneca obtained the exclusive right to develop, manufacture, and commercialize products containing linaclotide in the AstraZeneca License Territory (Note 6). In November 2019, AstraZeneca began commercializing LINZESS for the treatment of adults with IBS-C in China. ​ The Company and AbbVie are exploring ways to enhance the clinical profile of LINZESS by studying linaclotide in additional indications, populations and formulations to assess its potential to treat various conditions. In September 2020, based on the Phase IIIb data demonstrating efficacy and safety of LINZESS 290 mcg on the overall abdominal symptoms of bloating, pain and discomfort in adult patients with IBS-C, the U.S. FDA approved the Company’s Supplemental New Drug Application to include a more comprehensive description of the effects of LINZESS in its approved label. In June 2020 and July 2020, the United States Patent and Trademark Office granted patents covering the formulation of the 72 mcg dose of LINZESS and methods of using the formulation, respectively. The patents are expected to expire in 2031. ​ The Company and AbbVie were developing MD-7246, a delayed release formulation of linaclotide. In May 2020, the Company and AbbVie announced top-line data from a Phase II trial evaluating MD-7246 in adult patients with abdominal pain associated with irritable bowel syndrome with diarrhea. The Phase II trial did not meet its primary or key secondary endpoints. Based on these findings, the Company and AbbVie discontinued the development of MD-7246. ​ The Company was developing IW-3718, a gastric retentive formulation of a bile acid sequestrant, in a Phase III program. In September 2020, the Company announced that one of its two identical Phase III trials for the potential treatment of refractory gastroesophageal reflux disease (“refractory GERD”) did not meet the pre-specified criteria associated with a planned early efficacy assessment. Based on these findings, the Company is discontinuing development of IW-3718. In connection with this decision, the Company reduced its workforce by approximately 100 full-time employees. This workforce reduction affected both field-based and home-office employees, including the relevant general and administrative support functions. The Company substantially completed the reduction in its workforce in the fourth quarter of 2020 (Note 18). ​ Additionally, the Company periodically enters into co-promotion agreements to bolster its salesforce productivity. In August 2019, the Company entered into a disease education and promotional agreement with Alnylam Pharmaceuticals, Inc. (“Alnylam”) for Alnylam’s GIVLAARI ® ​ These and other agreements are more fully described in Note 6, Collaboration, License, Co-Promotion and Other Commercial Agreements, ​ On April 1, 2019, Ironwood completed the separation (the “Separation”) of its soluble guanylate cyclase (“sGC”) business, and certain other assets and liabilities, into Cyclerion Therapeutics, Inc (“Cyclerion”). The Separation was effected by means of a distribution of all of the outstanding shares of common stock, with no par value, of Cyclerion through a dividend of all outstanding shares of Cyclerion’s common stock, to Ironwood’s stockholders of record as of the close of business on March 19, 2019 (Note 3). ​ The Company was incorporated in Delaware on January 5, 1998 as Microbia, Inc. On April 7, 2008, the Company changed its name to Ironwood Pharmaceuticals, Inc. To date, the Company has dedicated a majority of its activities to the research, development and commercialization of linaclotide, as well as to the research and development of its other product candidates. Prior to the year ended December 31, 2019, the Company incurred net losses in each year since its inception in 1998. For the years ended December 31, 2020 and 2019, the Company recorded net income of approximately $106.2 million and approximately $21.5 million, respectively. As of December 31, 2020, the Company had an accumulated deficit of approximately $1.5 billion.

Summary of Significant Accounti

Summary of Significant Accounting Policies	12 Months Ended
	Dec. 31, 2020
Disclosure Text Block
Summary of Significant Accounting Policies	2. Summary of Significant Accounting Policies Principles of Consolidation The accompanying consolidated financial statements include the accounts of Ironwood and its wholly-owned subsidiaries, as of December 31, 2020, Ironwood Pharmaceuticals Securities Corporation and Ironwood Pharmaceuticals GmbH. Cyclerion was a wholly-owned subsidiary until it became an independent publicly-traded company on April 1, 2019. All intercompany transactions and balances are eliminated in consolidation. ​ Segment Information Operating segments are components of an enterprise for which separate financial information is available and is evaluated regularly by the Company’s chief operating decision-maker in deciding how to allocate resources and in assessing performance. The Company currently operates in one reportable business segment—human therapeutics. Reclassifications ​ Certain prior period financial statement items have been reclassified to conform to current period presentation. ​ Discontinued Operations ​ The Company determined that its sGC business, which was disposed on April 1, 2019, met the criteria for classification as a discontinued operation in accordance with Accounting Standards Codification (“ASC”) Subtopic 205-20, Discontinued Operations Cyclerion Separation ​ Use of Estimates The preparation of consolidated financial statements in accordance with U.S. generally accepted accounting principles requires the Company’s management to make estimates and judgments that may 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 amounts of revenues and expenses during the reported periods. On an ongoing basis, the Company’s management evaluates its estimates, judgments and methodologies. Significant estimates and assumptions in the consolidated financial statements include those related to revenue recognition; accounts receivable; inventory valuation and related reserves; useful lives of long-lived assets, impairment of long-lived assets, including its acquired intangible assets and goodwill; valuation procedures for right-of-use assets and operating lease liabilities; valuation procedures for the issuance and repurchase of convertible notes; balance sheet classification of convertible notes; valuation of assets and liabilities held for disposition and losses related to discontinued operations; fair value of derivatives; income taxes, including the valuation allowance for deferred tax assets; research and development expenses; contingencies and share-based compensation. The Company bases its estimates on historical experience and on various other assumptions that are believed to be reasonable, the results of which form the basis for making judgments about the carrying values of assets and liabilities. Actual results may differ materially from these estimates under different assumptions or conditions. Changes in estimates are reflected in reported results in the period in which they become known. Cash and Cash Equivalents The Company considers all highly liquid investment instruments with a remaining maturity when purchased of three months or less to be cash equivalents. Investments qualifying as cash equivalents primarily consist of money market funds, U.S. government-sponsored securities, and repurchase agreements. The carrying amount of cash equivalents approximates fair value. The amount of cash equivalents included in cash and cash equivalents was approximately $349.0 million and approximately $177.0 million at December 31, 2020 and 2019, respectively. Restricted Cash The Company is contingently liable under unused letters of credit with a bank, related to the Company’s facility lease and vehicle lease agreements, in the amount of approximately $2.2 million as of December 31, 2020 and 2019. The Company records as restricted cash the collateral used to secure these letters of credit. The amount of restricted cash included in current assets and non-current assets was approximately $1.7 million and $0.5 million at December 31, 2020, respectively. The amount of restricted cash in current assets and non-current assets was approximately $1.2 million and $1.0 million at December 31, 2019, respectively. Concentrations of Suppliers The Company relies on its collaboration partners and their suppliers to manufacture linaclotide API, linaclotide finished drug product, and finished goods. If any of the Company’s collaboration partners and their suppliers were to limit or terminate production or otherwise fail to meet the quality or delivery requirements needed to satisfy the supply commitments, the process of locating and qualifying alternate sources could require up to several months, during which time production could be delayed. Such delays could have a material adverse effect on the Company’s business, financial position and results of operations. Accounts Receivable and Related Valuation Account The Company makes judgments as to its ability to collect outstanding receivables and provides an allowance for credit losses when collection becomes doubtful. Provisions are made based upon a specific review of all significant outstanding invoices and the overall quality and age of those invoices not specifically reviewed. The Company’s receivables relate primarily to amounts reimbursed under its collaboration, license and co-promotion agreements. The Company believes that credit risks associated with these partners are not significant. The Company reviews the need for an allowance for credit losses for its receivables based on various factors including payment history and historical bad debt experience. The Company had no allowance for credit losses as of December 31, 2020 or 2019. Concentrations of Credit Risk Financial instruments that subject the Company to credit risk primarily consist of cash and cash equivalents, restricted cash, and accounts receivable. The Company maintains its cash and cash equivalent balances with high-quality financial institutions and the Company believes that such funds are subject to minimal credit risk. The Company has adopted an investment policy which limits the amounts the Company may invest in certain types of investments, and requires all investments held by the Company to be at least AA- rated, thereby reducing credit risk exposure. Accounts receivable primarily consist of amounts due under the linaclotide collaboration agreement with AbbVie for North America (Note 6). The Company does not obtain collateral for its accounts receivable. The Company previously reflected amounts due from Allergan, net of amounts payable to Allergan, prior to its acquisition by AbbVie as related party accounts receivable, net. Following the acquisition of Allergan by AbbVie, the Company determined that AbbVie is not a related party to the Company (Note 17). The percentages of revenue recognized from significant collaborative partners of the Company in the years ended December 31, 2020, 2019 and 2018 as well as the account receivable balances, net of any payables due, at December 31, 2020 and 2019 are included in the following table: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Accounts ​ Revenue ​ ​ December 31, ​ Year Ended December 31, ​ 2020 2019 2020 2019 2018 Collaborative Partner: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ AbbVie (North America and Europe) 76 % 90 % 96 % 78 % 77 % Astellas (Japan) 1 % 8 % 1 % 13 % 20 % ​ For the years ended December 31, 2020, 2019 and 2018, no additional customers accounted for more than 10% of the Company’s revenue. ​ Property and Equipment ​ Property and equipment, including leasehold improvements, are recorded at cost, and are depreciated when placed into service using the straight-line method based on their estimated useful lives as follows: ​ ​ ​ ​ ​ ​ Estimated Useful Life Asset Description (In Years) Laboratory equipment 5 ​ Computer and office equipment 3 ​ Furniture and fixtures 7 ​ Software 3 ​ ​ Included in property and equipment are certain costs of software obtained for internal use. Costs incurred during the preliminary project stage are expensed as incurred, while costs incurred during the application development stage are capitalized and amortized over the estimated useful life of the software. The Company also capitalizes costs related to specific upgrades and enhancements when it is probable the expenditures will result in additional functionality. Maintenance and training costs related to software obtained for internal use are expensed as incurred. Leasehold improvements are amortized over the shorter of the estimated useful life of the asset or the lease term. Costs for capital assets not yet placed into service have been capitalized as construction in process, and will be depreciated in accordance with the above guidelines once placed into service. Maintenance and repair costs are expensed as incurred. ​ Finite Lived Intangible Assets The Company records the fair value of purchased intangible assets with finite useful lives as of the transaction date of a business combination. Purchased intangible assets with finite useful lives are amortized to their estimated residual values over their estimated useful lives. The value of the Company’s finite-lived intangible assets was based on the future expected net cash flows related to ZURAMPIC and DUZALLO (the “Lesinurad Products”), which included significant assumptions around future net sales and the respective investment to support these products. During the year ended December 31, 2018, the Company recorded an impairment charge of approximately $151.8 million to fully write-off its ZURAMPIC and DUZALLO intangible assets. ​ Impairment of Long-Lived Assets The Company regularly reviews the carrying amount of its long-lived assets to determine whether indicators of impairment may exist, which warrant adjustments to carrying values or estimated useful lives. If indications of impairment exist, projected future undiscounted cash flows associated with the asset are compared to the carrying amount to determine whether the asset’s value is recoverable. If the carrying value of the asset exceeds such projected undiscounted cash flows, the asset will be written down to its estimated fair value. ​ Income Taxes The Company provides for income taxes under the asset and liability method. Deferred tax assets and liabilities are determined based on differences between financial reporting and tax bases of assets and liabilities and are measured using the enacted tax rates in effect when the differences are expected to reverse. Deferred tax assets are reduced by a valuation allowance to reflect the uncertainty associated with their ultimate realization. The Company accounts for uncertain tax positions recognized in the consolidated financial statements in accordance with the provisions of ASC Topic 740, Income Taxes ​ Financing Costs Financing costs include costs directly attributable to the Company’s offerings of its equity securities and its debt financings. Costs attributable to equity offerings are charged as a reduction to stockholders’ equity against the proceeds of the offering once the offering is completed. Costs attributable to debt financings are deferred and amortized to interest expense over the term of the debt using the effective interest method. Costs incurred in connection with convertible debt securities are allocated between the liability and equity components. In accordance with ASC 835, Interest Leases Effective January 1, 2019, the Company adopted ASC Topic 842, Leases optional transition method ​ As part of the ASC 842 adoption, the Company elected certain practical expedients, which include: ​ ● Accounting policy election to use the short-term lease exception by asset class; and ● Election of the practical expedient package during transition, which includes: o An entity need not reassess whether any expired or existing contracts are or contain leases. o An entity need not reassess the classification for any expired or existing leases. As a result, all leases that were classified as operating leases in accordance with ASC 840 are classified as operating leases under ASC 842, and all leases that were classified as capital leases in accordance with ASC 840 are classified as finance leases under ASC 842. o An entity need not reassess initial direct costs for any existing leases. ​ Subsequent to the Company’s adoption of ASC 842, the Company elected the post-transition practical expedient, by class of underlying asset, to account for lease components and non-lease components together as a single component for the asset class of operating lease right-of-use real estate assets. ​ The Company’s lease portfolio for the year ended December 31, 2020 included: a lease for its headquarters location, a data center colocation lease, vehicle leases for its salesforce representatives, and leases for computer and office equipment. The Company determines if an arrangement is a lease at the inception of the contract. The asset component of the Company’s operating leases is recorded as operating lease right-of-use assets, and the liability component is recorded as current portion of operating lease liabilities and operating lease liabilities, net of current portion in the Company’s consolidated balance sheets. As of December 31, 2020, the Company did not record any finance leases. ​ Right-of-use assets and operating lease liabilities are recognized based on the present value of lease payments over the lease term at the lease inception date. Existing leases in the Company’s lease portfolio as of the adoption date were valued as of January 1, 2019. The Company uses an incremental borrowing rate based on the information available at lease inception in determining the present value of lease payments, if an implicit rate of return is not provided with the lease contract. Operating lease right-of-use assets are adjusted for incentives expected to be received. ​ Right-of-use assets and operating lease liabilities are remeasured upon certain modifications to leases using the present value of remaining lease payments and estimated incremental borrowing rate upon lease modification. ​ Lease cost is recognized on a straight-line basis over the lease term, and includes amounts related to short-term leases. The Company recognizes variable lease payments as operating expenses in the period in which the obligation for those payments is incurred. Variable lease payments primarily include common area maintenance, utilities, real estate taxes, insurance, and other operating costs that are passed on from the lessor in proportion to the space leased by the Company. ​ Derivative Assets and Liabilities In June 2015, the Company issued 2.25% Convertible Senior Notes due June 15, 2022 (the “2022 Convertible Notes”) and in August 2019, the Company issued 0.75% Convertible Senior Notes due 2024 (the “2024 Convertible Notes”) and 1.50% Convertible Senior Notes due 2026 (the “2026 Convertible Notes”) (together with the “2022 Convertible Notes” and the “2024 Convertible Notes”, the “Convertible Senior Notes”). In June 2015, in connection with the issuance of the 2022 Convertible Notes, the Company entered into convertible note hedge transactions (the “Convertible Note Hedges”). Concurrently with entering into the Convertible Note Hedges, the Company also entered into certain warrant transactions in which it sold note hedge warrants (the “Note Hedge Warrants”) to the Convertible Note Hedge counterparties to acquire shares of the Company’s Class A Common Stock, subject to customary anti-dilution adjustments (Note 11). In connection with the partial repurchase of the 2022 Convertible Notes in August 2019, the Company terminated its Convertible Note Hedges and Note Hedge Warrants proportionately. These instruments are derivative financial instruments under ASC Topic 815, Derivatives and Hedging These derivatives are recorded as assets or liabilities at fair value each reporting date and the fair value is determined using the Black-Scholes option-pricing model. The changes in fair value are recorded as a component of other (expense) income in the consolidated statements of operations. Significant inputs used to determine the fair value include the price per share of the Company’s Class A Common Stock on the date of valuation, expected term of the derivative instruments, strike prices of the derivative instruments, risk-free interest rate, and expected volatility of the Company’s Class A Common Stock. Changes to these inputs could materially affect the valuation of the Convertible Note Hedges and Note Hedge Warrants in future periods. In August 2019, in connection with the issuance of the 2024 Convertible Notes and the 2026 Convertible Notes, the Company entered into the Capped Calls. The Capped Calls cover the same number of shares of Class A Common Stock that initially underlie the 2024 Convertible Notes and the 2026 Convertible Notes (subject to anti-dilution and certain other adjustments). These instruments meet the conditions outlined in ASC 815 to be classified in stockholders’ equity (deficit) and are not subsequently remeasured as long as the conditions for equity classification continue to be met. ​ Revenue Recognition The Company’s revenues are generated primarily through collaborative arrangements and license agreements related to the research and development and commercialization of linaclotide, as well as co-promotion arrangements in the U.S. The terms of the collaborative research and development, license, co-promotion and other agreements contain multiple performance obligations which may include (i) licenses, (ii) research and development activities, including participation on joint steering committees, (iii) the manufacture of finished drug product, API, or development materials for a partner, which are reimbursed at a contractually determined rate, and (iv) education or co-promotion activities by the Company’s clinical sales specialists. Non-refundable payments to the Company under these agreements may include (i) up-front license fees, (ii) payments for research and development activities, (iii) payments for the manufacture of finished drug product, API, or development materials, (iv) payments based upon the achievement of certain milestones, (v) payments for sales detailing, promotional support services and medical education initiatives, and (vi) royalties on product sales. The Company receives its share of the net profits or bears its share of the net losses from the sale of linaclotide in the U.S. through its collaboration agreement with AbbVie for North America. The Company has adopted a policy to recognize revenue net of tax withholdings, as applicable. Collaboration, License, Co-Promotion and Other Commercial Agreements Upon licensing intellectual property to a customer, the Company determines if the license is distinct from the other performance obligations identified in the arrangement. The Company recognizes revenues from the transaction price, including non-refundable, up-front fees allocated to the license when the license is transferred to the customer if the license has distinct benefit to the customer. For licenses that are combined with other promises, the Company assesses the nature of the combined performance obligation to determine whether the combined performance obligation is satisfied over time or at a point in time. For performance obligations that are satisfied over time, the Company evaluates the measure of progress each reporting period and, if necessary, adjusts the measure of performance and related revenue recognition. The Company’s license and collaboration agreements include milestone payments, such as development and other milestones. The Company evaluates whether the milestones are considered probable of being reached and estimates the amount to be included in the transaction price using the most likely amount method at the inception of the agreement. If it is probable that a significant revenue reversal would not occur, the associated milestone value is included in the transaction price. Milestone payments that are not within the control of the Company, such as regulatory approvals, are not considered probable of being achieved until those approvals are received. The transaction price is then allocated to each performance obligation on a relative standalone selling price basis, for which the Company recognizes revenue as or when the performance obligations under the contract are satisfied. The Company re-evaluates the probability of achievement of such milestones and any related constraint at each reporting period, and any adjustments are recorded on a cumulative catch-up basis. Agreements that include the supply of API or drug product for either clinical development or commercial supply at the customer’s discretion are generally considered as options. The Company assesses if these options provide a material right to its partner, and if so, they are accounted for as separate performance obligations. If the Company is entitled to additional payments when the customer exercises these options, any additional payments are recorded as revenue when the customer obtains control of the goods, which is typically upon shipment for sales of API and finished drug product. For agreements that include sales-based royalties, including milestone payments based on the level of sales, and the license is deemed to be the predominant item to which the royalties relate, the Company recognizes revenue when the related sales occur. Net Profit or Net Loss Sharing In accordance with ASC 808 Topic, Collaborative Arrangements Revenue from Contracts with Customers The Company’s collaborative arrangements revenues generated from sales of LINZESS in the U.S. are considered akin to sales-based royalties. In accordance with the sales-based royalty exception, the Company recognizes its share of the pre-tax commercial net profit or net loss generated from the sales of LINZESS in the U.S. in the period the product sales are earned, as reported by AbbVie, and related cost of goods sold and selling, general and administrative expenses as incurred by the Company and AbbVie. These amounts are partially determined based on amounts provided by AbbVie and involve the use of estimates and judgments, such as product sales allowances and accruals related to prompt payment discounts, chargebacks, governmental and contractual rebates, wholesaler fees, product returns, and co-payment assistance costs, which could be adjusted based on actual results in the future. The Company is highly dependent on AbbVie for timely and accurate information regarding net revenues from sales of LINZESS in the U.S. in accordance with both ASC 808 and ASC 606, and the related costs, in order to accurately report its results of operations. If the Company does not receive timely and accurate information or incorrectly estimates activity levels associated with the collaboration at a given point in time, the Company could be required to record adjustments in future periods. In accordance with ASC 606-10-55, Principal Agent Considerations Product Revenue, Net Product revenue consisted of sales of the Lesinurad Products, in the U.S. until the termination of the exclusive license to develop, manufacture, and commercialize in the U.S. products containing lesinurad as an active ingredient (the “Lesinurad License”) in January 2019. The Company sold the Lesinurad Products principally to a limited number of national wholesalers and selected regional wholesalers (the “Distributors”). The Distributors resold the Lesinurad Products to retail pharmacies and healthcare providers, who then sold to patients. Net product revenue was recognized when the Distributor obtained control of the Company’s product, which occurred at a point in time, typically upon shipment of Lesinurad Products to the Distributor. When the Company performed shipping and handling activities after the transfer of control to the Distributor (e.g., when control transfers prior to delivery), they were considered fulfillment activities, and accordingly, the costs were accrued for when the related revenue was recognized. The Company expensed incremental costs of obtaining a contract as and when incurred if the expected amortization period of the asset that the Company would have recognized was one year or less. The Company evaluated the creditworthiness of each of its Distributors to determine whether it was probable that a significant reversal in the amount of the cumulative revenue recognized would not occur. The Company calculated its net product revenue based on the wholesale acquisition cost that the Company charged its Distributors for the Lesinurad Products less variable consideration. The product revenue variable consideration consisted of estimates relating to (i) trade discounts and allowances, such as invoice discounts for prompt payment and distributor fees, (ii) estimated government and private payor rebates, chargebacks and discounts, such as Medicaid reimbursements, (iii) reserves for expected product returns and (iv) estimated costs of incentives offered to certain indirect customers including patients. These estimates would be adjusted based on actual results in the period such variances became known. Product revenue was recorded net of the trade discounts, allowances, rebates, chargebacks, discounts, product returns, and other incentives. Certain of these adjustments were recorded as an accounts receivable reserve, while certain of these adjustments were recorded as accrued expenses. ​ Sale of Active Pharmaceutical Ingredient During the years ended December 31, 2020, 2019, and 2018, the Company produced linaclotide API, finished drug product, finished goods, and/or development materials for certain of its partners. As of December 31, 2020, the Company is no longer responsible for the supply of linaclotide API, finished drug product, finished goods or development materials to its partners. As it relates to development materials and API produced for Astellas, the Company was reimbursed at a contracted rate. Such reimbursements were considered as part of revenue generated pursuant to the Astellas license agreement and are presented as collaborative arrangements revenue. Any linaclotide API, finished drug product, finished goods, and development materials AbbVie is responsible for producing for the U.S. are recognized in accordance with the cost-sharing provisions of the collaboration agreement with AbbVie for North America. Prior to the execution of the Amended AstraZeneca Agreement in September 2019, any linaclotide API, finished drug product, and development materials produced for AstraZeneca for China (including Hong Kong and Macau) were recognized in accordance with the cost-sharing provisions of the AstraZeneca collaboration agreement. The Company recognized revenue on linaclotide API, finished drug product, finished goods, and development materials when control has transferred to the partner, which generally occurs upon shipment after the material passed all quality testing required for acceptance by the partner. Other The Company’s deferred revenue balance consists of advance billings and payments received from customers in excess of revenue recognized. Cost of Revenues Cost of revenues includes cost related to the sales of linaclotide API and finished drug product, as well as the cost of product revenue related to sales of the Lesinurad Products in the U.S. Cost related to the sales of linaclotide API, finished drug product, and finished goods are generally recognized upon shipment to certain of the Company’s partners outside of the U.S. The Company’s cost of revenues for linaclotide consists of the internal and external costs of producing such API and finished drug product. Cost of product revenue related to the sales of the Lesinurad Products in the U.S. includes the cost of producing finished goods that correspond with product revenue for the reporting period, such as third-party supply and overhead costs, as well as certain period costs related to freight, packaging, stability and quality testing, and customer acquisition. Research and Development Costs The Company generally expenses research and development costs to operations as incurred. The Company capitalizes nonrefundable advance payments made by the Company for research and development activities and defers expense recognition until the related goods are received or the related services are performed. Research and development expenses are comprised of costs incurred in performing research and development activities, including salary, benefits, share-based compensation, and other employee-related expenses; laboratory supplies and other direct expenses; facilities expenses; overhead expenses; third-party contractual costs relating to nonclinical studies and clinical trial activities and related contract manufacturing expenses, development of manufacturing processes and regulatory registration of third-party manufacturing facilities; licensing fees for the Company’s product candidates; and other outside expenses. The Company has certain collaboration agreements pursuant to which it shares or has shared research and development expenses related to linaclotide. The Company records expenses incurred under such linaclotide collaboration arrangements as research and development expense. Prior to the execution of the Amended AstraZeneca Agreement in September 2019, under the Company’s collaboration agreement with AstraZeneca for China (including Hong Kong and Macau), the Company was reimbursed for certain research and development expenses and it netted these reimbursements against its research and development expenses as incurred. In connection with the execution of the Amended AstraZeneca Agreement, AstraZeneca is fully responsible for all research and development costs incurred related to the development, manufacture, and commercialization of linaclotide in China (including Hong Kong and Macau). Under the Company’s collaboration agreement with AbbVie for North America, the Company is reimbursed for certain research and development expenses and nets these reimbursements against its research and development expenses as incurred. Amounts owed to AbbVie or AstraZeneca under the Company’s respective collaboration agreements were recorded as incremental research and development expense. ​ Restructuring Expenses Restructuring expenses are comprised primarily of costs associated with exit and disposal activities in accordance with ASC 420, Exit or Disposal Cost Obligations Selling, General and Administrative Expenses The Company expenses selling, general and administrative costs to operations as incurred. Selling, general and administrative expenses consist primarily of compensation, benefits and other employee-related expenses for personnel in the Company’s administrative, finance, legal, information technology, business development, commercial, sales, marketing, communications and human resource functions. Other costs include the legal costs of pursuing patent protection of the Company’s intellectual property, general and administrative related facility costs, insurance costs and professional fees for accounting, tax, consulting, legal and other services. Prior to the execution of the Amended AstraZeneca Agreement, the Company was reimbursed for certain selling, general and administrative expenses and the Company netted these reimbursements against the Company’s selling, general and administrative expenses as incurred. In connection with the Amended AstraZeneca Agreement, effective in September 2019, AstraZeneca will be fully responsible for all costs related to the development, manufacture, and commercialization of linaclotide in China (including Hong Kong and Macau). The Company includes AbbVie’s selling, general and administrative cost-sharing payments in the calculation of the net profits and net losses from the sale of LINZESS in the U.S. and presents the net payment to or from AbbVie as collaboration expense or collaborative arrangements revenue, respectively. ​ Share-Based Compensation Expense The Company grants awards under its share-based compensation programs, including stock awards, restricted stock awards (“RSAs”), restricted stock units (“RSUs”) (including both time-based and performance-based RSUs), stock options, and shares issued under the Company’s employee stock purchase plan (“ESPP”). Share-based compensation is recognized as expense in the consolidated statements of operations based on the grant date fair value over the requisite service period, net of estimated forfeitures. The Com

Cyclerion Separation

Cyclerion Separation	12 Months Ended
	Dec. 31, 2020
Disclosure Text Block
Cyclerion Separation	​ 3. Cyclerion Separation ​ On April 1, 2019, Ironwood completed the separation of its sGC business, and certain other assets and liabilities, into Cyclerion. The Separation was effected by means of a distribution of all of the outstanding shares of common stock, with no par value, of Cyclerion through a dividend of Cyclerion’s common stock, to Ironwood’s stockholders of record as of the close of business on March 19, 2019. Prior to the Separation on April 1, 2019, as described in Note 1, Nature of Business ​ Agreements with Cyclerion ​ The separation agreement with Cyclerion, dated as of March 30, 2019, sets forth, among other things, the Company’s agreements with Cyclerion regarding the principal actions to be taken in connection with the Separation, including the dividend, which was effective as of April 1, 2019. The separation agreement identifies assets transferred, liabilities assumed by and contracts assigned to each of Cyclerion and Ironwood as part of the Separation, and provides for when and how these transfers, assumptions and assignments occur. The purpose of the separation agreement was to provide Cyclerion and Ironwood with assets to operate their respective businesses and retain or assume liabilities related to those assets. ​ The transfer of assets and liabilities to Cyclerion was effected through a contribution in accordance with the separation agreement as summarized below (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ As of April 1, 2019 ​ Assets: ​ ​ ​ ​ Prepaid expenses and other current assets ​ $ 1,169 ​ Property and equipment, net ​ ​ 10,241 ​ Other assets ​ ​ 21 ​ ​ ​ $ 11,431 ​ Liabilities: ​ ​ ​ ​ Accrued research and development costs ​ $ 5,673 ​ Accrued expenses and other current liabilities ​ ​ 3,149 ​ ​ ​ $ 8,822 ​ Net Assets Transferred to Cyclerion ​ $ 2,609 ​ ​ In addition, the Company received approximately $1.3 million during the year ended December 31, 2019 associated with tenant improvement reimbursement provisions related to the Cyclerion lease in accordance with the separation agreement. ​ The tax matters agreement, dated as of March 30, 2019, governs each party’s rights, responsibilities and obligations with respect to taxes, including taxes, if any, incurred as a result of any failure of the Separation to qualify as tax-free. In general, if the parties incur tax liabilities in the event that the Separation is not tax-free, each party is expected to be responsible for any taxes imposed on Ironwood or Cyclerion that arise from the failure of the Separation to qualify as a transaction that is generally tax-free for U.S. federal income tax purposes, under Sections 355 and 368(a)(1)(D) and certain other relevant provisions of the Internal Revenue Code of 1986, as amended, to the extent that the failure to so qualify is attributable to an acquisition of stock or assets of, or certain actions, omissions or failures to act of, such party. If both Ironwood and Cyclerion are responsible for such failure, liability will be shared according to relative fault. U.S. tax otherwise resulting from the failure of the Separation to qualify as a transaction that is tax-free generally will be the responsibility of Ironwood. Each party otherwise agreed to indemnify the other party from and against any liability for taxes allocated to such party under the tax matters agreement and any taxes resulting from breach of any such party’s covenants under the tax matters agreement, the separation agreement, or any ancillary agreement entered into in connection with the Separation. Cyclerion agreed to certain covenants that contain restrictions intended to preserve the tax-free status of the distribution and certain related transactions. ​ The employee matters agreement, dated as of March 30, 2019, allocates assets, liabilities and responsibilities relating to the employment, compensation, and employee benefits of Ironwood and Cyclerion employees, and other related matters in connection with the Separation, including the treatment of outstanding Ironwood incentive equity awards. Pursuant to the employee matters agreement, the outstanding Ironwood equity awards held by Cyclerion and Ironwood employees were adjusted in connection with the Separation, with the intent to maintain, immediately following the Separation, the economic value of the awards. No incremental stock-based compensation expense related to the Separation-related adjustments was recognized during the year ended December 31, 2019 (Note 14). ​ Additionally, the Company entered into two transition services agreements and a development agreement with Cyclerion. ​ Pursuant to the transition service agreements, the Company was obligated to provide and was entitled to receive certain transition services related to corporate functions, such as finance, procurement, facilities and development. As of December 31, 2020, both transition service agreements had terminated. Amounts received for services provided to Cyclerion were recorded as other income and amounts paid for services provided by Cyclerion were recorded as selling, general and administrative expense and research and development expense, as applicable. During the years ended December 31, 2020 and 2019, the Company recorded an insignificant amount and approximately $0.3 million, respectively, as other income for services provided to Cyclerion. During each of the years ended December 31, 2020 and 2019, the Company recorded an insignificant amount in both selling, general and administrative expense and research and development expense for services provided by Cyclerion, respectively. ​ Pursuant to the development agreement, Cyclerion is obligated to provide the Company with certain research and development services with respect to certain of Ironwood’s products and product candidates for an initial period of two years, unless earlier terminated or extended. Such research and development activities are governed by a joint steering committee comprised of representatives from both Cyclerion and Ironwood. Services received are paid at a mutually agreed upon rate. The Company recorded approximately $2.3 million and $4.5 million in research and development expenses under the development agreement during the years ended December 31, 2020 and 2019, respectively. The Company had an insignificant amount and approximately $1.5 million of accounts payable due to Cyclerion as of December 31, 2020 and 2019, respectively. ​ Discontinued Operations ​ Upon the Separation, the Company determined its sGC business qualified for discontinued operations accounting treatment in accordance with ASC 205-20. There were no discontinued operations during year ended December 31, 2020. The following is a summary of expenses of Cyclerion classified as discontinued operations for years ended December 31, 2019 and 2018 (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Year Ended December 31, ​ ​ 2019 2018 Costs and expenses: ​ ​ ​ ​ ​ ​ ​ Research and development ​ $ 21,792 ​ $ 65,443 ​ Selling, general and administrative ​ ​ 15,646 ​ 21,615 ​ Restructuring expenses ​ ​ — ​ ​ 1,164 ​ Net loss from discontinued operations ​ $ 37,438 ​ $ 88,222 ​ ​ There were no assets or liabilities related to discontinued operations as of either December 31, 2020 or December 31, 2019, as all balances were transferred to Cyclerion upon Separation.

Net Income (Loss) Per Share

Net Income (Loss) Per Share	12 Months Ended
	Dec. 31, 2020
Disclosure Text Block
Net Income (Loss) Per Share	4. Net Income (Loss) Per Share The following table sets forth the computation of basic and diluted net income (loss) per common share (in thousands, except per share amounts): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Year Ended December 31, ​ 2020 ​ 2019 2018 Numerator: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Net income (loss) ​ $ 106,176 ​ $ 21,505 ​ $ (282,368) ​ Denominator: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Weighted average number of common shares outstanding used in net income (loss) per share — basic ​ 159,427 ​ 156,023 ​ 152,634 ​ Effect of dilutive securities: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Stock options ​ ​ 367 ​ ​ — ​ ​ — ​ Time-based restricted stock units ​ ​ 766 ​ ​ — ​ ​ — ​ Performance-based restricted stock units ​ ​ 1 ​ ​ — ​ ​ — ​ Restricted stock ​ ​ 94 ​ ​ — ​ ​ — ​ Dilutive potential common shares ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Weighted average number of common shares outstanding used in net income (loss) per share — diluted ​ ​ 160,655 ​ 156,023 ​ ​ 152,634 ​ Net income (loss) per share — basic ​ ​ 0.67 ​ 0.14 ​ ​ (1.85) ​ Net income (loss) per share — diluted ​ $ 0.66 ​ $ 0.14 ​ $ (1.85) ​ ​ The outstanding securities have been excluded from the computation of diluted weighted average shares outstanding, as applicable, as their effect would be anti-dilutive (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Year Ended December 31, ​ 2020 2019 2018 Stock options 11,746 17,194 20,457 ​ Restricted stock awards 2 182 65 ​ Time-based restricted stock units ​ 209 ​ 3,207 ​ 3,058 ​ Performance-based restricted stock units ​ 93 ​ — ​ — ​ Note Hedge Warrants ​ 8,318 ​ 8,318 ​ 20,250 ​ 2022 Convertible Notes ​ 8,318 ​ 8,318 ​ 20,250 ​ 2024 Convertible Notes ​ 14,934 ​ 14,934 ​ — ​ 2026 Convertible Notes ​ 14,934 ​ 14,934 ​ — ​ ​ 58,554 67,087 64,080 ​ ​ The potentially dilutive impact of the 2022 Convertible Notes, 2024 Convertible Notes and 2026 Convertible notes (together, the “Convertible Senior Notes”) (Note 11) is determined using the treasury stock method. Under this method, no numerator or denominator adjustments arise from the principal and interest components of the Convertible Senior Notes because the Company has the intent and ability to settle the Convertible Senior Notes’ principal and interest in cash. Instead, the Company is required to increase the diluted net income (loss) per share denominator by the variable number of shares that would be issued upon conversion if it settled the conversion spread obligation with shares. For diluted net income (loss) per share purposes, the conversion spread obligation is calculated based on whether the average market price of the Company’s Class A Common Stock during the reporting period is in excess of the conversion price of the Convertible Senior Notes. There was no calculated spread added to the denominator for the years ended December 31, 2020, 2019, or 2018.

Goodwill and Intangible Assets

Goodwill and Intangible Assets	12 Months Ended
	Dec. 31, 2020
Disclosure Text Block
Goodwill and Intangible Assets	5. Goodwill and Intangible Assets ​ The Company closed a transaction with AstraZeneca (the “Lesinurad Transaction”) on June 2, 2016 (the “Acquisition Date”) pursuant to which the Company received an exclusive license to develop, manufacture and commercialize the Lesinurad Products in the U.S. In August 2018, the Company delivered to AstraZeneca a notice of termination of the lesinurad license agreement, which termination was made with respect to all products under the lesinurad license agreement. ​ The value of the developed technology – ZURAMPIC and developed technology – DUZALLO intangible assets as of the Acquisition Date was approximately $22.0 million and approximately $145.1 million, respectively. As of July 31, 2018, the accumulated amortization for developed technology – ZURAMPIC and developed technology – DUZALLO intangible assets was approximately $3.6 million and approximately $11.7 million, respectively. ​ During the year ended December 31, 2018, the Company completed its initiative to evaluate the optimal mix of investments for the lesinurad franchise for uncontrolled gout using a comprehensive marketing mix in select test markets (with paired controls). Data from the test markets did not meet expectations. As a result, during the year ended December 31, 2018, the Company reduced its projected revenue and net cash flow assumptions associated with the value of its developed technology – ZURAMPIC and developed technology – DUZALLO intangible assets. Accordingly, the Company evaluated its developed technology – ZURAMPIC and developed technology – DUZALLO intangible assets for impairment and recorded an approximately $151.8 million impairment charge during the year ended December 31, 2018. The impairment assessment performed utilized the revised projected revenue and net cash flows assumed through the termination of the lesinurad license agreement, resulting in an impairment of the full carrying value of the intangible assets. The impairment charge was recorded as impairment of intangible assets in the Company’s consolidated statement of operations. ​ The Company tests its goodwill for impairment annually as of October 1 st

Collaboration, License, Promoti

Collaboration, License, Promotion and Other Commercial Agreements	12 Months Ended
	Dec. 31, 2020
Disclosure Text Block
Collaboration, License, Promotion and Other Commercial Agreements	6. Collaboration, License, Co-Promotion and Other Commercial Agreements For the year ended December 31, 2020, the Company had linaclotide collaboration agreements with AbbVie for North America and AstraZeneca for China (including Hong Kong and Macau), as well as linaclotide license agreements with Astellas for Japan and with AbbVie for the AbbVie License Territory. The Company also had an agreement with Alnylam to perform disease awareness activities for AHP and sales detailing activities for GIVLAARI. The following table provides amounts included in the Company’s consolidated statements of operations as collaborative arrangements revenue and sale of API primarily attributable to transactions from these arrangements (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Year Ended December 31, Collaborative Arrangements Revenue 2020 2019 2018 Linaclotide Collaboration and License Agreements: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ AbbVie (North America) ​ $ 370,902 $ 327,591 $ 266,177 ​ AbbVie (Europe and other) ​ ​ 2,196 ​ ​ 1,718 ​ ​ 1,146 ​ AstraZeneca (China, including Hong Kong and Macau) ​ ​ 682 ​ 32,628 ​ — ​ Astellas (Japan) ​ ​ 2,128 ​ 10,147 ​ — ​ Co-Promotion and Other Agreements: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ AbbVie (VIBERZI) (1) ​ ​ — ​ ​ 3,723 ​ ​ 4,290 ​ Alnylam (GIVLAARI) ​ ​ 4,302 ​ ​ 2,000 ​ ​ — ​ Other ​ ​ 1,335 ​ ​ 1,845 ​ ​ 1,226 ​ Total collaborative arrangements revenue ​ $ 381,545 ​ $ 379,652 ​ $ 272,839 ​ Sale of API ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Linaclotide Agreements: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Astellas (Japan) ​ $ 2,017 ​ $ 45,788 ​ $ 69,599 ​ AstraZeneca (China, including Hong Kong and Macau) ​ ​ 5,540 ​ ​ 2,973 ​ ​ — ​ Other ​ ​ 421 ​ ​ — ​ ​ 756 ​ Total sale of API ​ $ 7,978 ​ $ 48,761 ​ $ 70,355 ​ (1) The Company had an agreement with AbbVie to perform sales detailing activities for VIBERZI® (eluxadoline) which terminated as of December 31, 2019. Accounts receivable, net, included approximately $145.8 million primarily related to collaborative arrangements revenue and sale of API, collectively, as of December 31, 2020, including approximately $110.9 million of accounts receivable, net, which includes approximately $4.3 million of accounts payable from the Company’s partner, AbbVie. Accounts receivable, net, included approximately $43.9 million related to collaborative arrangements revenue and sale of API, collectively, as of December 31, 2019. The Company previously reflected amounts due from Allergan prior to its acquisition by AbbVie in May 2020 as related party accounts receivable. As of December 31, 2019, related party accounts receivable, net, included approximately $110.1 million related to collaborative arrangements revenue, net of approximately $4.1 million of related party accounts payable. Following acquisition of Allergan by AbbVie, the Company determined that AbbVie is not a related party to the Company (Note 17). At December 31, 2019, deferred revenue was approximately $0.9 million related to the disease education and promotional agreement with Alnylam. At December 31, 2020, no deferred revenue was recorded. The Company routinely assesses the creditworthiness of its license and collaboration partners. The Company has not experienced any material losses related to receivables from its license or collaboration partners during the years ended December 31, 2020, 2019, or 2018. Linaclotide Agreements Collaboration Agreement for North America with AbbVie In September 2007, the Company entered into a collaboration agreement with AbbVie to develop and commercialize linaclotide for the treatment of IBS-C, CIC, and other GI conditions in North America. Under the terms of this collaboration agreement, the Company received a non-refundable, upfront licensing fee and shares equally with AbbVie all development costs as well as net profits or losses from the development and sale of linaclotide in the U.S. The Company receives royalties in the mid-teens percent based on net sales in Canada and Mexico. AbbVie is solely responsible for the further development, regulatory approval and commercialization of linaclotide in those countries and funding any costs. The collaboration agreement for North America also includes contingent milestone payments, as well as a contingent equity investment, based on the achievement of specific development and commercial milestones. At December 31, 2019, $205.0 million in license fees and all six development milestone payments had been received by the Company, as well as a $25.0 million equity investment in the Company’s capital stock. The Company can also achieve up to $80.0 million in a sales-related milestone if certain conditions are met, which will be recognized as collaborative arrangements revenue when it is probable that a significant reversal of revenue would not occur, and the associated constraints have been lifted. During the years ended December 31, 2020, 2019 and 2018, the Company incurred approximately $20.1 million, approximately $37.6 million, and approximately $39.2 million in total research and development expenses under the linaclotide collaboration for North America. As a result of the research and development cost-sharing provisions of the linaclotide collaboration for North America, the Company incurred approximately $5.6 million during the year ended December 31, 2020, and offset approximately $7.2 million and approximately $9.0 million in research and development costs during the years ended December 31, 2019 and 2018, respectively, to reflect the obligations of each party under the collaboration to bear 50% of the development costs incurred. The Company and AbbVie began commercializing LINZESS in the U.S. in December 2012. The Company receives 50% of the net profits and bears 50% of the net losses from the commercial sale of LINZESS in the U.S. Net profits or net losses consist of net sales of LINZESS to third-party customers and sublicense income in the U.S. less the cost of goods sold as well as selling, general and administrative expenses. LINZESS net sales are calculated and recorded by AbbVie and may include gross sales net of discounts, rebates, allowances, sales taxes, freight and insurance charges, and other applicable deductions. The Company evaluated its collaboration arrangement for North America with AbbVie and concluded that all development-period performance obligations had been satisfied as of September 2012. However, the Company has determined that there are three remaining commercial-period performance obligations, which include the sales detailing of LINZESS, participation in the joint commercialization committee, and approved additional trials. The consideration remaining includes cost reimbursements in the U.S., as well as commercial sales-based milestones and net profit and loss sharing payments based on net sales in the U.S. Additionally, the Company receives royalties in the mid-teens percent based on net sales in Canada and Mexico. Royalties, commercial sales-based milestones, and net profit and loss sharing payments will be recorded as collaborative arrangements revenue or expense in the period earned, as these payments relate predominately to the license granted to AbbVie. The Company records royalty revenue in the period earned based on royalty reports from its partner, if available, or based on the projected sales and historical trends. The cost reimbursements received from AbbVie during the commercialization period will be recognized as earned in accordance with the right-to-invoice practical expedient, as the Company’s right to consideration corresponds directly with the value of the services transferred during the commercialization period. Under the Company’s collaboration agreement with AbbVie for North America, LINZESS net sales are calculated and recorded by AbbVie and include gross sales net of discounts, rebates, allowances, sales taxes, freight and insurance charges, and other applicable deductions, as noted above. These amounts include the use of estimates and judgments, which could be adjusted based on actual results in the future. The Company records its share of the net profits or net losses from the sales of LINZESS in the U.S. on a net basis less commercial expenses, and presents the settlement payments to and from AbbVie as collaboration expense or collaborative arrangements revenue, as applicable. This treatment is in accordance with the Company’s revenue recognition policy, given that the Company is not the primary obligor and does not have the inventory risks in the collaboration agreement with AbbVie for North America. The Company relies on AbbVie to provide accurate and complete information related to net sales of LINZESS in accordance with U.S. generally accepted accounting principles in order to calculate its settlement payments to and from AbbVie and record collaboration expense or collaborative arrangements revenue, as applicable. From time to time, in accordance with the terms of the collaboration with AbbVie for North America, the Company engages an independent certified public accounting firm to review the accuracy of the financial reporting from AbbVie to the Company. In connection with such a review during the three months ended September 30, 2018, AbbVie reported to the Company an approximately $59.3 million negative adjustment to LINZESS net sales. The adjustment related to the cumulative difference between certain previously estimated LINZESS gross-to-net sales reserves and allowances made by AbbVie during the years ended December 31, 2015, 2016 and 2017, and subsequent actual payments made. This adjustment was primarily associated with estimated governmental and contractual rebates, as reported by AbbVie. Upon receiving this information from AbbVie, the Company recorded a change in accounting estimate to reduce collaborative arrangements revenue by approximately $29.7 million during the three months ended September 30, 2018 related to the Company’s share of this adjustment. In addition, during the three months ended December 31, 2018, AbbVie reported to the Company a true-up of approximately $0.2 million related to the previously reported adjustment for the cumulative difference between certain previously estimated LINZESS gross-to-net sales reserves and allowances. ​ The Company recognized collaborative arrangements revenue from the AbbVie collaboration agreement for North America during the years ended December 31, 2020, 2019, and 2018 as follows (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Year Ended December 31, ​ 2020 2019 2018 Collaborative arrangements revenue related to sales of LINZESS in the U.S. ​ $ 368,603 ​ $ 325,429 ​ $ 264,243 ​ Royalty revenue ​ 2,299 ​ 2,162 ​ 1,934 ​ Total collaborative arrangements revenue ​ $ 370,902 ​ $ 327,591 ​ $ 266,177 ​ ​ The collaborative arrangements revenue recognized in the years ended December 31, 2020, 2019, and 2018 primarily represents the Company’s share of the net profits and net losses on the sale of LINZESS in the U.S. The following table presents the amounts recorded by the Company for commercial efforts related to LINZESS in the U.S. in the years ended December 31, 2020, 2019, and 2018 (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Year Ended December 31, ​ 2020 2019 2018 Ironwood's collaborative arrangement revenue ​ $ 368,603 ​ $ 325,429 ​ $ 264,243 ​ Selling, general and administrative costs incurred by the Company (1) ​ (39,312) ​ (38,123) ​ (42,435) ​ Ironwood's share of net profits (2) ​ $ 329,291 ​ $ 287,306 ​ $ 221,808 ​ ​ (1) Includes Ironwood’s selling, general and administrative expenses attributable to the cost-sharing arrangement with AbbVie. Excludes approximately $0.6 million, approximately $2.4 million, and approximately $2.2 million for the years ended December 31, 2020, 2019, and 2018 respectively, related to patent prosecution and patent litigation costs recognized in connection with the collaboration agreement with AbbVie. (2) Ironwood has recalculated its share of net profit on sales of LINZESS in the U.S. to conform with AbbVie’s recast of historically reported LINZESS U.S. net sales (previously reported by Allergan). In May 2014, CONSTELLA ® License Agreement with AbbVie (All countries other than the countries and territories of North America, China (including Hong Kong and Macau), and Japan) In April 2009, the Company entered into a license agreement with Almirall, S.A. (“Almirall”) to develop and commercialize linaclotide in Europe (including the Commonwealth of Independent States and Turkey) for the treatment of IBS-C, CIC and other GI conditions (the “European License Agreement”). In accordance with the European License Agreement, the Company granted Almirall a right to access its U.S. Phase III clinical trial data for the purposes of supporting European regulatory approval. In October 2015, Almirall transferred its exclusive license to develop and commercialize linaclotide in Europe to AbbVie. Additionally, in October 2015, the Company and AbbVie separately entered into an amendment to the European License Agreement relating to the development and commercialization of linaclotide in Europe. Pursuant to the terms of the amendment, (i) certain sales-based milestones payable to the Company under the European License Agreement were modified to increase the total milestone payments such that, when aggregated with certain commercial launch milestones, they could total up to $42.5 million, (ii) the royalties payable to the Company during the term of the European License Agreement were modified such that the royalties based on sales volume in Europe begin in the mid-single digit percent and escalate to the upper-teens percent by calendar year 2019, and (iii) AbbVie assumed responsibility for the manufacturing of linaclotide API for Europe from the Company, as well as the associated costs. The Company concluded that the 2015 amendment to the European License Agreement was not a modification to the linaclotide collaboration agreement with AbbVie for North America. In January 2017, the Company and AbbVie entered into an amendment to the European License Agreement (the “2017 Amendment”). The 2017 Amendment extended the license to develop and commercialize linaclotide in all countries other than China (including Hong Kong and Macau), Japan, and the countries and territories of North America. On a country-by-country and product-by-product basis in such additional territory, AbbVie is obligated to pay the Company a royalty as a percentage of net sales of products containing linaclotide as an active ingredient in the upper-single digits for five years following the first commercial sale of a linaclotide product in a country, and in the low-double digits thereafter. The royalty rate for products in the expanded territory will decrease, on a country-by-country basis, to the lower-single digits, or cease entirely, following the occurrence of certain events. The 2017 Amendment did not modify any of the milestones or royalty terms related to Europe. In evaluating the terms of the European License Agreement, as amended, the Company determined that there are no remaining performance obligations as of September 2012. However, the Company continues to be eligible to receive consideration in the form of commercial launch milestones, sales-based milestones, and royalties. The commercial launch milestones, sales-based milestones and royalties under the European License Agreement and the 2017 Amendment relate predominantly to the license granted to AbbVie. The Company records royalties on sales of CONSTELLA in Europe in the period earned based on royalty reports from its partner, if available, or the projected sales and historical trends under the sales-based royalty exception. The commercial launch milestones are recognized as revenue when it is probable that a significant reversal of revenue would not occur and the associated constraint has been lifted. The Company recognized approximately $2.2 million, approximately $1.7 million and approximately $1.1 million of royalty revenue from the Amended European License Agreement during the years ended December 31, 2020, 2019, and 2018, respectively. License Agreement for Japan with Astellas In November 2009, the Company entered into a license agreement with Astellas, as amended, to develop and commercialize linaclotide for the treatment of IBS-C, CIC and other GI conditions in Japan (the “2009 License Agreement with Astellas”). Astellas is responsible for all activities relating to development, regulatory approval and commercialization in Japan as well as funding the associated costs and the Company was required to participate on a joint development committee over linaclotide’s development period. During the year ended December 31, 2017, the Company and Astellas entered into a commercial API supply agreement (the “Astellas Commercial Supply Agreement”). Pursuant to the Astellas Commercial Supply Agreement, the Company sells linaclotide API supply to Astellas at a contractually defined rate and recognizes related revenue as sale of API. Under the 2009 License Agreement with Astellas, the Company received royalties which escalated based on sales volume, beginning in the low-twenties percent, less the transfer price paid for the API included in the product sold and other contractual deductions. Under the 2009 License Agreement with Astellas, the Company received an up-front licensing fee of $30.0 million and three development milestone payments that totaled $45.0 million, which were recognized as revenue prior to the adoption of ASC 606 on January 1, 2018. The Company evaluated the terms of the 2009 License Agreement with Astellas and determined that there were no remaining performance obligations as of the adoption of ASC 606. Additionally, under the terms of the Astellas Commercial Supply Agreement, the Company determined it had an ongoing performance obligation to supply API. During the years ended December 31, 2019 and 2018, the Company recognized revenue of approximately $27.5 million and approximately $69.6 million, respectively, from the sale of API to Astellas under the 2009 License Agreement with Astellas and the Astellas Commercial Supply Agreement. The royalties on sales of LINZESS in Japan did not exceed the transfer price of API sold and other contractual deductions during each of the periods presented. In August 2019, the Company and Astellas amended and restated the 2009 License Agreement with Astellas (the “Amended Astellas License Agreement”). This amendment to the 2009 License Agreement with Astellas was accounted for as a separate contract. Under the terms of the Amended Astellas License Agreement, the Company is no longer responsible for the supply of linaclotide API to Astellas, and Astellas assumed responsibility for its own supply of linaclotide API in Japan in 2020. ​ In connection with the execution of the Amended Astellas License Agreement, Astellas paid the Company a non-refundable, upfront payment of $10.0 million in August 2019. Further, Astellas, in lieu of the royalty payment terms set forth in the 2009 License Agreement with Astellas, pays royalties to the Company at rates beginning in the mid-single digit percent and escalating to low-double-digit percent, based on aggregate annual net sales in Japan of products containing linaclotide API. These royalty payments are subject to reduction following the expiration of certain licensed patents and the occurrence of generic competition in Japan. The Company continued to supply linaclotide API for Japan during 2019 and 2020 at a contractually defined rate. Additionally, Astellas reimbursed the Company for the Company’s performance of adverse event reporting services at a fixed monthly rate until such services were terminated in February 2020. ​ The Company identified the following performance obligations under the Amended Astellas License Agreement: ​ ● delivery of the expanded license of intellectual property, including the applicable manufacturing know-how; ● obligation to supply linaclotide API for 2019; and ● adverse event reporting services. ​ The Company allocated the $10.0 million upfront payment to the delivery of the expanded license of intellectual property and recognized it as collaborative arrangements revenue at contract inception. The Company allocated the approximately $20.4 million in remaining purchase orders for API to the obligation to supply linaclotide API to Astellas for 2019. Consideration for the supply of linaclotide API is recognized over the performance period as linaclotide API is shipped to Astellas. Consideration allocated to the adverse event reporting services is recognized as such services are provided over the performance period based on the amount to which the Company has a right to invoice. ​ Royalties on sales of LINZESS in Japan relate predominantly to the license granted to Astellas. Accordingly, the Company applies the sales-based royalty exception and records royalties on sales of LINZESS in Japan in the period earned based on royalty reports from its partner, if available, or the projected sales and historical trends. ​ The Company recognized $10.0 million in collaborative arrangements revenue during the year ended December 31, 2019 related to the upfront fee associated with the execution of the Amended Astellas License Agreement. The Company recognized approximately $2.0 million and approximately $18.3 million from the sale of API to Astellas under the Amended License Agreement during the years ended December 31, 2020 and 2019, respectively. The Company recognized approximately $2.1 million of royalty revenue during the year ended December 31, 2020. The Company recognized an insignificant amount of collaborative arrangements revenue related to adverse event reporting services in each of the years ended December 31, 2020 and 2019. ​ Collaboration Agreement for China (including Hong Kong and Macau) with AstraZeneca In October 2012, the Company entered into a collaboration agreement with AstraZeneca to co-develop and co-commercialize linaclotide in the AstraZeneca License Territory (the “AstraZeneca Collaboration Agreement”). The collaboration provided AstraZeneca with an exclusive nontransferable license to exploit the underlying technology in the AstraZeneca License Territory. The parties shared responsibility for continued development and commercialization of linaclotide under a joint development plan and a joint commercialization plan, respectively, with AstraZeneca having primary responsibility for the local operational execution. In September 2019, the Company and AstraZeneca entered into an amendment and restatement of the AstraZeneca Collaboration Agreement (the “Amended AstraZeneca Agreement”) under which AstraZeneca obtained the exclusive right to develop, manufacture and commercialize products containing linaclotide in the AstraZeneca License Territory (the “AstraZeneca License”). Prior to the execution of the Amended AstraZeneca Agreement, the Company identified the following performance obligations under the AstraZeneca Collaboration Agreement: ● research, development and regulatory services pursuant to the development plan (“R&D Services”); ● Joint Development Committee (“JDC”) services; ● obligation to supply clinical trial material; and ● Joint Commercialization Committee services. Under the original AstraZeneca Collaboration Agreement, the Company shared development costs with AstraZeneca, with AstraZeneca incurring 55% of the net losses from the development and commercialization of linaclotide in the AstraZeneca License Territory. Payments from AstraZeneca with respect to both research and development and selling, general and administrative costs incurred by the Company prior to the commercialization of linaclotide in the AstraZeneca License Territory were recorded as a reduction in expense. Development costs incurred by the Company that pertained to the joint development plan and subsequent amendments to the joint development plan, as approved by the JDC, were recorded as research and development expense as incurred. Payments to AstraZeneca were recorded as incremental research and development expense. During the years ended December 31, 2019 and 2018, the Company incurred approximately $1.2 million and approximately $0.9 million, respectively, related to pre-launch commercial services and supply chain services. Under the Amended AstraZeneca Agreement, the Company is entitled to receive non-contingent payments totaling $35.0 million in three installments through 2024, of which $10.0 million was received in January 2021. In addition, AstraZeneca may be required to make milestone payments totaling up to $90.0 million contingent on the achievement of certain sales targets and will be required to pay tiered royalties to the Company at rates beginning in the mid-single-digit percent and increasing up to twenty percent based on the aggregate annual net sales of products containing linaclotide in the AstraZeneca License Territory. In connection with the Amended AstraZeneca Agreement, the Company and AstraZeneca entered into a transition services agreement (“AstraZeneca TSA”) and an amended commercial supply agreement (“AstraZeneca CSA”). Under the terms of the AstraZeneca TSA, the Company will provide certain regulatory and administrative services for a term of approximately two years from the date of execution, unless earlier terminated or extended. Services performed are paid at a mutually agreed upon rate. Amounts for AstraZeneca TSA services are recorded as collaborative arrangements revenue. Under the terms of the AstraZeneca CSA, the Company supplied linaclotide API, finished drug product and finished goods for the Licensed Territory through March 31, 2020 at predetermined rates. The Company evaluated the Amended AstraZeneca Agreement and determined that it would be accounted for as a separate contract because it adds a distinct good or service at an amount that reflects standalone selling price. The following performance obligations under the Amended AstraZeneca Agreement were identified: ● delivery of the expanded AstraZeneca License; ● AstraZeneca TSA services; and ● supply of linaclotide API, finished drug product and finished goods under the AstraZeneca CSA. The Company determined that the non-contingent payments should be allocated to the delivery of the expanded AstraZeneca License. The Company determined that the performance obligation related to the transfer of the AstraZeneca License was satisfied as of the execution date of the Amended AstraZeneca Agreement. As a portion of the payments relating to the transfer of the AstraZeneca License are due significantly after the performance obligation was satisfied, the Company adjusted its transaction price for the significant financing component of approximately $2.6 million. Accordingly, the Company recognized approximately $32.4 million relating to the delivery of the AstraZeneca License as collaborative arrangements revenue at contract inception and will recognize the approximately $2.6 million relating to the significant financing component as interest income through 2024 using the effective interest method. Consideration allocated to the AstraZeneca TSA services will be recognized as collaborative arrangements revenue as such services are provided over the performance period based on the amount to which the Company has a right to invoice. Consideration for the supply of linaclotide API, finished drug product and finished goods under the AstraZeneca CSA was recognized over the performance period as linaclotide API, finished drug product and finished goods were shipped to AstraZeneca. During the year ended December 31, 2020, the Company recognized approximately $0.7 million in collaborative arrangements revenue related to the Amended AstraZeneca License, of which approximately $0.6 million related to the AstraZeneca TSA services and approximately $0.1 million related to royalties. During the year ended December 31, 2020, the Company recognized approximately $5.5 million of sale of API on its consolidated statement of operations relating to the supply of linaclotide finished drug product and finished goods under the AstraZeneca CSA. During the year ended December 31, 2019, the Company recognized approximately $32.6 million in collaborative arrangements revenue related to the Amended AstraZeneca License, of which approximately $32.4 million related to the delivery of the AstraZeneca License and approximately $0.2 million related to the AstraZeneca TSA services. During the year ended December 31, 2019, the Company recognized approximately $3.0 million of sale of API on its consolidated statement of operations relating to the supply of linaclotide finished drug product and finished goods under the AstraZeneca CSA. Co-Promotion and Other Agreements Disease Education and Promotional Agreement with Alnylam In August 2019, the Company and Alnylam entered into a disease education and promotional agreement for Alnylam’s GIVLAARI, and this agreement was subsequently amended in December 2020 (the “Alnylam Agreement”). GIVLAARI was approved by the U.S. FDA in November 2019 for the treatment of adult patients with AHP. Under the terms of the Alnylam Agreement, the Company’s sales force is performing disease awareness activities and sales detailing activities for GIVLAARI to gastroenterologists and health care practitioners to whom they detail LINZESS in the first position over the term of the agreement, which is approximately three years. Under the Alnylam Agreement, the Company received service fees, totaling approximately $5.5 million for services rendered through December 31, 2020. The Company also is eligible to receive royalties based on a percentage of net sales of GIVLAARI that are directly attributable to the Company’s promotional efforts over the term of the agreement. The Company identified the following performance obligation under the Alnylam Agreement: ● performance of disease education activities for AHP and performance of sales details for GIVLAARI (together “Givosiran Education and Promotion Activities”). The Company allocated the service fees to the performance of Givosiran Education and Promotion Activities and recognized collaborative arrangements revenue through December 31, 2020 as the services were performed based on the amount to which the Company had a right to invoice. Royalties are recognized as collaborative arrangements revenue for Givosiran Education and Promotion Activities based on the amount to which the Company has a right to invoice when the associated constraints have been lifted. During the years ended December 31, 2020 and 2019, the Company recognized approximately $3.5 million and approximately $2.0 million, respectively, in collaborative arrangements revenue related to the service fees. During the year ended December 31, 2020, the Company recognized approximately $0.8 million in royalty revenue related to the Alnylam Agreement. The Company did not approximately $0.9 million related to advance billings of service fees. As of December 31, 2020, the Company had no deferred revenue.

Fair Value of Financial Instrum

Fair Value of Financial Instruments	12 Months Ended
	Dec. 31, 2020
Disclosure Text Block
Fair Value of Financial Instruments	7. Fair Value of Financial Instruments The tables below present information about the Company’s assets that are measured at fair value on a recurring basis as of December 31, 2020 and 2019 and indicate the fair value hierarchy of the valuation techniques the Company utilized to determine such fair value. In general, fair values determined by Level 1 inputs utilize observable inputs such as quoted prices in active markets for identical assets or liabilities. Fair values determined by Level 2 inputs utilize data points that are either directly or indirectly observable, such as quoted prices for similar instruments in active markets, interest rates and yield curves. Fair values determined by Level 3 inputs utilize unobservable data points in which there is little or no market data, which require the Company to develop its own assumptions for the asset or liability. The Company’s investment portfolio may include fixed income securities that do not always trade on a daily basis. As a result, the pricing services used by the Company apply other available information as applicable through processes such as benchmark yields, benchmarking of like securities, sector groupings and matrix pricing to prepare valuations. In addition, model processes are used to assess interest rate impact and develop prepayment scenarios. These models take into consideration relevant credit information, perceived market movements, sector news and economic events. The inputs into these models may include benchmark yields, reported trades, broker-dealer quotes, issuer spreads and other relevant data. The Company validates the prices provided by its third party pricing services by obtaining market values from other pricing sources and analyzing pricing data in certain instances. The Company also invests in certain reverse repurchase agreements, which are collateralized by Government Securities and Obligations for an amount not less than 102% of their principal amount. The Company does not record an asset or liability for the collateral as the Company is not permitted to sell or re-pledge the collateral. The collateral has at least the prevailing credit rating of U.S. Government Treasuries and Agencies. The Company utilizes a third party custodian to manage the exchange of funds and ensure the collateral received is maintained at 102% of the reverse repurchase agreements principal amount on a daily basis. The following tables present the assets and liabilities the Company has measured at fair value on a recurring basis (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Fair Value Measurements at Reporting Date Using ​ ​ ​ Quoted Prices in Significant Other Significant ​ ​ ​ ​ ​ Active Markets for ​ Observable ​ Unobservable ​ ​ December 31, ​ Identical Assets ​ Inputs ​ Inputs ​ ​ 2020 ​ (Level 1) ​ (Level 2) ​ (Level 3) ​ Assets: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Cash and cash equivalents: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Money market funds ​ $ 349,014 ​ $ 349,014 ​ $ — ​ $ — ​ Restricted cash: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Money market funds ​ ​ 2,221 ​ ​ 2,221 ​ ​ — ​ ​ — ​ Convertible note hedges ​ ​ 13,065 ​ ​ — ​ ​ — ​ ​ 13,065 ​ Total assets measured at fair value ​ $ 364,300 ​ $ 351,235 ​ $ — ​ $ 13,065 ​ Liabilities: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Note hedge warrants ​ $ 12,088 ​ $ — ​ $ — ​ $ 12,088 ​ Total liabilities measured at fair value ​ $ 12,088 ​ $ — ​ $ — ​ $ 12,088 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Fair Value Measurements at Reporting Date Using ​ ​ ​ Quoted Prices in Significant Other Significant ​ ​ ​ ​ ​ Active Markets for ​ Observable ​ Unobservable ​ ​ December 31, ​ Identical Assets ​ Inputs ​ Inputs ​ ​ 2019 ​ (Level 1) ​ (Level 2) ​ (Level 3) ​ Assets: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Cash and cash equivalents: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Money market funds ​ $ 139,190 ​ $ 139,190 ​ $ — ​ $ — ​ Repurchase agreements ​ ​ 37,800 ​ ​ 37,800 ​ ​ — ​ ​ — ​ Restricted cash: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Money market funds ​ 2,221 ​ 2,221 ​ — ​ — ​ Convertible note hedges ​ ​ 31,366 ​ ​ — ​ ​ — ​ ​ 31,366 ​ Total assets measured at fair value ​ $ 210,577 ​ $ 179,211 ​ $ — ​ $ 31,366 ​ Liabilities: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Note hedge warrants ​ $ 24,260 ​ $ — ​ $ — ​ $ 24,260 ​ Total liabilities measured at fair value ​ $ 24,260 ​ $ — ​ $ — ​ $ 24,260 ​ ​ There were no transfers between fair value measurement levels during each of the years ended December 31, 2020 or 2019. Cash equivalents, accounts receivable, related party accounts receivable, prepaid expenses and other current assets, accounts payable, related party accounts payable, accrued research and development costs, accrued expenses and other current liabilities, current portion of operating lease obligations, and deferred revenue at December 31, 2020 and 2019 are carried at amounts that approximate fair value due to their short-term maturities. Convertible Note Hedges and Note Hedge Warrants with Respect to 2022 Convertible Notes The Company’s Convertible Note Hedges and the Note Hedge Warrants are recorded as derivative assets and liabilities, respectively, and are classified as Level 3 measurements under the fair value hierarchy. These derivatives are not actively traded and are valued using the Black-Scholes option-pricing model, which requires the use of subjective assumptions. Significant inputs used to determine the fair value as of December 31, 2020 included the price per share of the Company’s Class A Common Stock, expected terms of the derivative instruments, strike prices of the derivative instruments, risk-free interest rates, and expected volatility of the Company’s Class A Common Stock. Changes to these inputs could materially affect the valuation of the Convertible Note Hedges and Note Hedge Warrants. The following inputs were used in the fair market valuation of the Convertible Note Hedges and Note Hedge Warrants as of December 31, 2020 and 2019: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, ​ December 31, ​ ​ 2020 ​ 2019 ​ ​ ​ Convertible Note Hedge ​ Convertible Note Hedge ​ ​ Note Hedges ​ Warrants Note Hedges ​ Warrants Risk-free interest rate (1) ​ ​ 0.1 % ​ 0.1 % ​ 1.6 % ​ 1.6 % Expected term ​ 1.5 ​ 2.0 ​ ​ 2.5 ​ 3.0 ​ Stock price (2) ​ $ 11.39 ​ $ 11.39 ​ $ 13.31 ​ $ 13.31 ​ Strike price (3) ​ $ 14.51 ​ $ 18.82 ​ $ 14.51 ​ $ 18.82 ​ Common stock volatility (4) ​ ​ 46.7 % ​ 50.3 % ​ 49.1 % ​ 46.5 % Dividend yield (5) ​ — % — % — % — % (1) Based on U.S. Treasury yield curve, with terms commensurate with the expected terms of the Convertible Note Hedges and the Note Hedge Warrants. (2) The closing price of the Company’s Class A Common Stock on the last trading days of the years ended December 31, 2020 and 2019, respectively. (3) As per the respective agreements for the Convertible Note Hedges and Note Hedge Warrants. (4) Expected volatility based on historical volatility of the Company’s Class A Common Stock. (5) The Company has not paid and does not anticipate paying cash dividends on its shares of common stock in the foreseeable future; therefore, the expected dividend yield is assumed to be zero . ​ The Convertible Note Hedges and the Note Hedge Warrants are recorded at fair value at each reporting date and changes in fair value are recorded in other (expense) income, net within the Company's consolidated statements of operations. The following table reflects the change in the Company's Level 3 Convertible Note Hedges and Note Hedge Warrants from December 31, 2018 through December 31, 2020 (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Convertible ​ Note Hedge ​ ​ Note Hedges Warrants Balance at December 31, 2018 ​ $ 41,020 ​ $ (33,763) ​ Cash settlement (received) paid upon early termination of derivatives (Note 11) ​ ​ (28,909) ​ ​ 25,735 ​ Change in fair value, recorded as a component of gain (loss) on derivatives ​ ​ 19,255 ​ ​ (16,232) ​ Balance at December 31, 2019 ​ $ 31,366 ​ $ (24,260) ​ Change in fair value, recorded as a component of (loss) gain on derivatives ​ ​ (18,301) ​ ​ 12,172 ​ Balance at December 31, 2020 ​ $ 13,065 ​ $ (12,088) ​ ​ Convertible Senior Notes In June 2015, the Company issued approximately $335.7 million aggregate principal amount of its 2022 Convertible Notes. In August 2019, the Company issued $200.0 million aggregate principal amount of its 2024 Convertible Notes and $200.0 million aggregate principal amount of its 2026 Convertible Notes, and used a portion of the proceeds from such issuances to repurchase $215.0 million aggregate principal amount of its 2022 Convertible Notes. The Company separately accounted for the liability and equity components of each of the 2022 Convertible Notes, 2024 Convertible Notes, and 2026 Convertible Notes, by allocating the proceeds between the liability component and equity component (Note 11). The fair value of the respective convertible senior notes, which differs from their carrying value, is influenced by interest rates, the price of the Company’s Class A Common Stock and the volatility thereof, and the prices for the respective convertible senior notes observed in market trading, which are Level 2 inputs. The estimated fair value of the 2022 Convertible Notes as of December 31, 2020 and 2019 was approximately $130.2 million and $141.3 million, respectively. The estimated fair value of the 2024 Convertible Notes as of December 31, 2020 and 2019 was approximately $222.3 million and $235.7 million, respectively. The estimated fair value of the 2026 Convertible Notes as of December 31, 2020 and 2019 was approximately $224.1 million and $240.1 million, respectively. Capped Calls with Respect to 2024 Convertible Notes and 2026 Convertible Notes ​ In connection with the issuance of the 2024 Convertible Notes and the 2026 Convertible Notes, the Company entered into the Capped Calls with certain financial institutions. The Capped Calls cover 29,867,480 shares of Class A Common Stock (subject to anti-dilution and certain other adjustments), which is the same number of shares of Class A Common Stock that initially underlie the 2024 Convertible Notes and the 2026 Convertible Notes. The Capped Calls have an initial strike price of approximately $13.39 per share, which corresponds to the initial conversion price of the 2024 Convertible Notes and the 2026 Convertible Notes, and have a cap price of approximately $17.05 per share (Note 11). The strike price and cap price are subject to anti-dilution adjustments generally similar to those applicable to the 2024 Convertible Notes and the 2026 Convertible Notes. These instruments meet the conditions outlined in ASC 815 to be classified in stockholders’ equity (deficit) and are not subsequently remeasured as long as the conditions for equity classification continue to be met (Note 11).

Leases

Leases	12 Months Ended
	Dec. 31, 2020
Disclosure Text Block
Leases	8. Leases Effective January 1, 2019, the Company adopted ASC 842 using the optional transition method ​ Lease cost is recognized on a straight-line basis over the lease term. The components of lease cost for the year ended December 31, 2020 and 2019 are as follows (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Year Ended December 31, ​ ​ ​ 2020 ​ 2019 ​ Operating lease cost during period, net (1) ​ $ 2,530 ​ $ 16,452 ​ Variable lease payments ​ ​ — ​ ​ 1,526 ​ Short-term lease cost ​ ​ 1,420 ​ ​ 1,512 ​ Total lease cost ​ $ 3,950 ​ $ 19,490 ​ (1) Operating lease cost is presented net of approximately $0.3 million of sublease income for the year ended December 31, 2019 related to a sublease agreement between Ironwood and Cyclerion executed upon Separation. The sublease agreement terminated in May 2019. ​ Supplemental cash flow information related to leases for the periods reported is as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Year Ended December 31, ​ ​ ​ 2020 ​ 2019 ​ Right-of-use assets obtained in exchange for new operating lease upon adoption of ASC 842 (in thousands) ​ $ — ​ ​ $ 88,299 ​ ​ Adjustment to right-of-use assets as a result of the lease modification upon Separation (in thousands) ​ ​ — ​ ​ ​ (40,427) ​ ​ Adjustment to right-of-use assets as a result of the termination of the Binney Street Lease (in thousands) ​ ​ — ​ ​ ​ (34,440) ​ ​ Right-of-use assets obtained in exchange for new operating lease liabilities upon execution of Summer Street Lease (in thousands) ​ ​ — ​ ​ ​ 18,452 ​ ​ Cash paid for amounts included in the measurement of lease liabilities (in thousands) ​ ​ 1,146 ​ ​ ​ 18,598 ​ ​ Weighted-average remaining lease term of operating leases (in years) ​ ​ 9.3 ​ ​ ​ 10.2 ​ ​ Weighted-average discount rate of operating leases ​ ​ 5.8 % ​ ​ 5.8 % ​ ​ Future minimum lease payments under non-cancelable operating leases as of December 31, 2020 are as follows (in thousands): ​ ​ ​ ​ ​ ​ Operating ​ Lease ​ ​ Payments 2021 ​ $ 3,128 2022 ​ ​ 3,129 2023 ​ ​ 3,065 2024 ​ ​ 3,126 2025 ​ 3,189 2026 and thereafter ​ 14,856 Total future minimum lease payments ​ ​ 30,493 Less: present value adjustment ​ ​ (7,047) Operating lease liabilities at December 31, 2020 ​ ​ 23,446 Less: current portion of operating lease liabilities ​ ​ (3,128) Operating lease liabilities, net of current portion ​ $ 20,318 ​ Summer Street Lease (current headquarters) ​ In June 2019, the Company entered into a non-cancelable operating lease (the “Summer Street Lease”) for approximately 39,000 square feet of office space on the 23 rd additional five years at a market base rental rate. The rent expense, inclusive of the escalating rent payments and lease incentives, is recognized on a straight-line basis over the lease term. Additionally, the Summer Street Lease requires a letter of credit to secure the Company’s obligations under the lease agreement of approximately $1.0 million, which is collateralized by a money market account recorded as restricted cash on the Company’s consolidated balance sheet as of December 31, 2020. ​ At lease inception, the Company recorded a right-of-use asset and a lease liability associated with the Summer Street Lease using an incremental borrowing rate of approximately 5.8%. At December 31, 2020, the balances of the right-of-use asset and operating lease liability were approximately $16.6 million and approximately $23.2 million, respectively. At December 31, 2019, the balances of the right-of-use asset and operating lease liability were approximately $17.7 million and approximately $22.8 million, respectively. ​ Lease costs related to the Summer Street Lease recorded during the years ended December 31, 2020 and 2019 were approximately $2.5 million and approximately $1.5 million, respectively. ​ Binney Street Lease (prior headquarters) ​ The Company rented office space at 301 Binney Street, Cambridge, Massachusetts under a non-cancelable operating lease entered into in January 2007, as amended (“Binney Street Lease”) through October 2019. ​ On April 1, 2019, the Company modified the Binney Street Lease to reduce its leased premises to approximately 108,000 rentable square feet of office space on the first and third floors. The surrendered portion of approximately 114,000 rentable square feet on the first and second floor of the building was subsequently occupied by Cyclerion under a direct lease between Cyclerion and the Binney Street landlord. As a result of the modification, the Company adjusted the value of its right-of-use asset and operating lease liability using an incremental borrowing rate of approximately 5.1%, and recognized a gain of approximately $3.2 million, which was recorded as a reduction to operating expenses on its consolidated statement of operations. The Company elected to determine the proportionate reduction in the right-of-use asset based on the reduction to the lease liability. ​ As of January 1, 2019, in conjunction with the adoption of ASC 842, the Company recorded a right-of-use asset of approximately $87.7 million and a lease liability of approximately $94.3 million associated with the Binney Street Lease. ​ On June 11, 2019, the Company entered into a lease termination agreement (the “Lease Termination”) with the Binney Street landlord to terminate the Company’s lease for approximately 108,000 square feet of office space. The Lease Termination was effective during the fourth quarter of 2019 in exchange for an approximately $9.0 million payment. The Lease Termination was accounted for as a lease modification that reduces the term of the existing lease and the Company adjusted the value of its right-of-use asset and operating lease liability using an incremental borrowing rate of approximately 4.0%. ​ Lease cost related to the Binney Street Lease recorded during the year ended December 31, 2019 was approximately $16.3 million, net of sublease income of approximately $0.3 million. Under ASC 840, rent expense related to the Binney Street Lease recorded during the year ended December 31, 2018 was approximately $10.0 million. ​ Vehicle fleet leases ​ During April 2018, the Company entered into a master services agreement containing 12-month leases (the “2018 Vehicle Leases”) for vehicles within its fleet for its field-based sales force and medical science liaisons. These leases are classified as short-term in accordance with the practical expedient in ASC 842. The 2018 Vehicle Leases expire at varying times, with a monthly ​ Lease cost related to the 2018 Vehicle Leases was approximately $1.4 million and approximately $1.5 million, respectively, for the years ended December 31, 2020 and 2019. Under ASC 840, lease cost related to the 2018 Vehicle Leases was approximately $0.8 million for the year ended December 31, 2018.

Property and Equipment

Property and Equipment	12 Months Ended
	Dec. 31, 2020
Disclosure Text Block
Property and Equipment	9. Property and Equipment Property and equipment, net consisted of the following (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, ​ 2020 2019 Software ​ $ 8,615 ​ $ 9,568 ​ Leasehold improvements ​ 7,407 ​ 7,318 ​ Laboratory equipment ​ 1,898 ​ 2,193 ​ Furniture and fixtures ​ 1,517 ​ 1,508 ​ Computer and office equipment ​ 1,297 ​ 1,293 ​ Construction in process ​ — ​ 631 ​ ​ ​ 20,734 ​ 22,511 ​ Less accumulated depreciation and amortization ​ (11,805) ​ (10,082) ​ ​ ​ $ 8,929 ​ $ 12,429 ​ ​ Depreciation expense of property and equipment was approximately $2.3 million and $5.6 million for the years ended December 31, 2020 and 2019, respectively. Depreciation and amortization expense of property and equipment, including amounts recorded under capital leases under ASC 840, was approximately $3.9 million for the year ended December 31, 2018. During the year ended December 31, 2020, the Company recorded approximately $1.2 million in restructuring expenses in its consolidated statement of operations related to the impairment of certain fixed assets as a result of its decision to discontinue IW-3718 development.

Accrued Expenses and Other Curr

Accrued Expenses and Other Current Liabilities	12 Months Ended
	Dec. 31, 2020
Disclosure Text Block
Accrued Expenses and Other Current Liabilities	10. Accrued Expenses and Other Current Liabilities Accrued expenses and other current liabilities consisted of the following (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, ​ 2020 2019 Accrued incentive compensation ​ $ 8,719 ​ $ 11,760 ​ Accrued vacation ​ ​ 2,625 ​ ​ 2,540 ​ Professional fees ​ 530 ​ 1,421 ​ Salaries ​ ​ 627 ​ ​ 2,973 ​ Other employee benefits ​ ​ 1,442 ​ ​ 1,260 ​ Restructuring liabilities ​ ​ 10,510 ​ ​ 179 ​ Other ​ 2,033 ​ 10,332 ​ ​ ​ $ 26,486 ​ $ 30,465 ​ ​ As of December 31, 2020, other accrued expenses of approximately $2.0 million included approximately $1.6 million of uninvoiced vendor liabilities and approximately $0.3 million of accrued interest. ​ As of December 31, 2019, other accrued expenses of approximately $10.3 million included approximately $4.1 million related to API batches uninvoiced, approximately $0.9 million related to activities associated with the Company’s move to the 100 Summer Street headquarters, approximately $0.6 million related to unbilled inventory, approximately $0.3 million of accrued interest, and approximately $0.2 million related to equipment for clinical studies.

Notes Payable

Notes Payable	12 Months Ended
	Dec. 31, 2020
Disclosure Text Block
Notes Payable	11. Notes Payable 8.375% Notes due 2026 ​ On September 23, 2016, the Company closed a direct private placement, pursuant to which the Company issued $150.0 million in aggregate principal amount of 8.375% Notes due 2026 (the “2026 Notes”) and received net proceeds of approximately $11.2 million. The Company capitalized approximately $0.5 million of debt issuance costs, which were netted against the carrying value of the 2026 Notes. Proceeds from the issuance of the 2024 Convertible Notes and the 2026 Convertible Notes were used, in part, to redeem the outstanding principal balance of the 2026 Notes in September 2019. The Company retired the 2026 Notes, which had an outstanding aggregate principal balance of approximately $116.5 million, for a redemption price of approximately $123.0 million. The redemption of the 2026 Notes resulted in a loss on extinguishment of debt of approximately $7.6 million related to the prepayment premium and write-off of the unamortized debt issuance costs and unamortized debt discount. ​ The 2026 Notes had an annual interest rate of 8.375%, with interest payable March 15, June 15, September 15 and December 15 of each year (each an “8.375% Payment Date”). Principal of the 2026 Notes was payable on the 8.375% Payment Dates beginning March 15, 2019. From March 15, 2019, the Company made quarterly payments on the 2026 Notes equal to the greater of (i) 7.5% of net sales of linaclotide in the U.S. for the preceding quarter (the “8.375% Synthetic Royalty Amount”) and (ii) accrued and unpaid interest on the 2026 Notes (the “8.375% Required Interest Amount”). Principal on the 2026 Notes was due to be repaid in an amount equal to the 8.375% Synthetic Royalty Amount minus the 8.375% Required Interest Amount, when this was a positive number, until the principal had been paid in full. ​ Convertible Senior Notes 2.25% Convertible Senior Notes due 2022 In June 2015, the Company issued approximately $335.7 million aggregate principal amount of the 2022 Convertible Notes. The Company received net proceeds of approximately $324.0 million from the sale of the 2022 Convertible Notes, after deducting fees and expenses of approximately $11.7 million. The Company used approximately $21.1 million of the net proceeds from the sale of the 2022 Convertible Notes to pay the net cost of the Convertible Note Hedges (after such cost was partially offset by the proceeds to the Company from the sale of the Note Hedge Warrants), as described below. The 2022 Convertible Notes are governed by an indenture (the “2022 Indenture”) between the Company and U.S. Bank National Association, as trustee (the “Trustee”). The 2022 Convertible Notes are senior unsecured obligations and bear cash interest at the annual rate of 2.25%, payable on June 15 and December 15 of each year. The 2022 Convertible Notes will mature on June 15, 2022, unless earlier converted or repurchased. The Company may settle conversions of the 2022 Convertible Notes through payment or delivery, as the case may be, of cash, shares of the Company’s Class A Common Stock or a combination of cash and shares of Class A Common Stock, at the Company’s option (subject to, and in accordance with, the settlement provisions of the 2022 Indenture). The initial conversion rate for the 2022 Convertible Notes was 60.3209 shares of Class A Common Stock (subject to adjustment as provided for in the 2022 Indenture) per $1,000 principal amount of the 2022 Convertible Notes, which was equal to an initial conversion price of approximately $16.58 per share and 20,249,665 shares. In connection with the Separation, in April 2019, the conversion rate under the 2022 Indenture was adjusted to equal 68.9172 shares of Class A Common Stock per $1,000 principal amount of the 2022 Convertible Notes, which is equal to an adjusted conversion price of approximately $14.51 per share and 23,135,435 shares. ​ Holders of the 2022 Convertible Notes may convert their 2022 Convertible Notes at their option at any time prior to the close of business on the business day immediately preceding December 15, 2021 in multiples of $1,000 principal amount, only under the following circumstances: ● during any calendar quarter commencing after the calendar quarter ending on September 30, 2015 (and only during such calendar quarter), if the last reported sale price of the Company’s Class A Common Stock for at least 20 trading days (whether or not consecutive) during a period of 30 consecutive trading days ending on the last trading day of the immediately preceding calendar quarter is greater than or equal to 130% of the conversion price for the 2022 Convertible Notes on each applicable trading day; ● during the five business day period after any five consecutive trading day period (the “measurement period”) in which the “trading price” (as defined in the 2022 Indenture) per $1,000 principal amount of the 2022 Convertible Notes for each trading day of the measurement period was less than 98% of the product of the last reported sale price of the Company’s Class A Common Stock and the conversion rate for the 2022 Convertible Notes on each such trading day; or ● upon the occurrence of specified corporate events described in the 2022 Indenture. On or after December 15, 2021, until the close of business on the second scheduled trading day immediately preceding June 15, 2022, holders may convert their 2022 Convertible Notes, in multiples of $1,000 principal amount, at the option of the holder regardless of the foregoing circumstances. The Company may not redeem the 2022 Convertible Notes prior to the maturity date and no “sinking fund” is provided for by the 2022 Convertible Notes, which means that the Company is not required to periodically redeem or retire the 2022 Convertible Notes. Upon the occurrence of certain fundamental changes involving the Company, holders of the 2022 Convertible Notes may require the Company to repurchase for cash all or part of their 2022 Convertible Notes at a repurchase price equal to 100% of the principal amount of the 2022 Convertible Notes to be repurchased, plus accrued and unpaid interest. If a make-whole fundamental change, as described in the 2022 Indenture, occurs and a holder elects to convert its 2022 Convertible Notes in connection with such make-whole fundamental change, such holder may be entitled to an increase in the conversion rate as described in the 2022 Indenture. The 2022 Indenture does not contain any financial covenants or restrict the Company’s ability to repurchase the Company’s securities, pay dividends or make restricted payments in the event of a transaction that substantially increases the Company’s level of indebtedness. The 2022 Indenture provides for customary events of default. In the case of an event of default with respect to the 2022 Convertible Notes arising from specified events of bankruptcy or insolvency, all outstanding 2022 Convertible Notes will become due and payable immediately without further action or notice. If any other event of default with respect to the 2022 Convertible Notes under the 2022 Indenture occurs or is continuing, the Trustee or holders of at least 25% in aggregate principal amount of the then outstanding 2022 Convertible Notes may declare the principal amount of the 2022 Convertible Notes to be immediately due and payable. Notwithstanding the foregoing, the 2022 Indenture provides that, upon the Company’s election, and for up to 180 days, the sole remedy for an event of default relating to certain failures by the Company to comply with certain reporting covenants in the 2022 Indenture consists exclusively of the right to receive additional interest on the 2022 Convertible Notes. In accordance with accounting guidance for debt with conversion and other options, the Company separately accounted for the liability and equity components of the 2022 Convertible Notes by allocating the proceeds between the liability component and the embedded conversion option, or equity component, due to the Company's ability to settle the 2022 Convertible Notes in cash, its Class A Common Stock, or a combination of cash and Class A Common Stock at the option of the Company. The carrying amount of the liability component was calculated by measuring the fair value of a similar liability that does not have an associated conversion feature. The equity component of the 2022 Convertible Notes was recognized as a debt discount and represents the difference between the gross proceeds from the issuance of the 2022 Convertible Notes and the fair value of the liability component of the 2022 Convertible Notes on their respective dates of issuance. The debt discount is amortized to interest expense using the effective interest method over seven years, or the expected life of the 2022 Convertible Notes. The equity component is not remeasured as long as it continues to meet the conditions for equity classification. ​ In connection with the issuance of the 2024 Convertible Notes and the 2026 Convertible Notes in August 2019, the Company repurchased $215.0 million aggregate principal amount of the 2022 Convertible Notes. The 2022 Convertible Notes were repurchased at a premium totaling approximately $227.3 million. The Company recognized a loss on extinguishment of debt of approximately $23.4 million during the year ended December 31, 2019 related to the prepayment premium and proportional write-off of the 2022 Convertible Notes unamortized debt issuance costs and unamortized debt discount. Additionally, the repurchase resulted in a reduction to additional paid-in capital of approximately $27.0 million during the year ended December 31, 2019 related to the equity component of the 2022 Convertible Notes. ​ 0.75% Convertible Senior Notes due 2024 and 1.50% Convertible Senior Notes due 2026 ​ In August 2019, the Company issued $200.0 million aggregate principal amount of the 2024 Convertible Notes and $200.0 million aggregate principal amount of the 2026 Convertible Notes. The Company received net proceeds of approximately $391.0 million from the sale of the 2024 Convertible Notes and 2026 Convertible Notes, after deducting fees and expenses of approximately $9.0 million. The Company used approximately $25.2 million of the net proceeds from the sale of the 2024 Convertible Notes and 2026 Convertible Notes to pay the cost of the Capped Calls, as described below. For purposes of this section, “Notes” refer to the 2024 Convertible Notes and the 2026 Convertible Notes, collectively. ​ The 2024 Convertible Notes and 2026 Convertible Notes were issued by the Company on August 12, 2019, pursuant to separate Indentures, each dated as of such date (each an “Indenture” and together the “Indentures”), between the Company and the Trustee. The 2024 Convertible Notes bear cash interest at the annual rate of 0.75% and the 2026 Convertible Notes bear cash interest at the annual rate of 1.50%, each payable on June 15 and December 15 of each year. The 2024 Convertible Notes will mature on June 15, 2024 and the 2026 Convertible Notes will mature on June 15, 2026, unless earlier converted or repurchased. The Company will settle conversions of the 2024 Convertible Notes and 2026 Convertible Notes through payment or delivery, as the case may be, of cash, shares of the Company’s Class A Common Stock or a combination of cash and shares of Class A Common Stock, at the Company’s option (subject to, and in accordance with, the settlement provisions of the applicable Indenture). The initial conversion rate for each of the 2024 Convertible Notes and the 2026 Convertible Notes is 74.6687 shares of Class A Common Stock (subject to adjustment as provided for in the applicable Indenture) per $1,000 principal amount of the 2024 Convertible Notes and 2026 Convertible Notes, which is equal to an initial conversion price of approximately $13.39 per share. ​ Holders of the 2024 Convertible Notes and 2026 Convertible Notes may convert their Notes at their option at any time prior to the close of business on the business day immediately preceding December 15, 2023, with respect to the 2024 Convertible Notes, and December 15, 2025, with respect to the 2026 Convertible Notes, in multiples of $1,000 principal amount, only under the following circumstances: ​ ● during any calendar quarter commencing after the calendar quarter ending on December 31, 2019 (and only during such calendar quarter), if the last reported sale price of Class A Common Stock for at least 20 trading days (whether or not consecutive) during a period of 30 consecutive trading days ending on the last trading day of the immediately preceding calendar quarter is greater than or equal to 130% of the conversion price for the Notes on each applicable trading day; ​ ● during the five business day period after any five consecutive trading day period (the “measurement period”) in which the “trading price” (as defined in each Indenture) per $1,000 principal amount of Notes for each trading day of the measurement period was less than 98% of the product of the last reported sale price of Class A Common Stock and the conversion rate for the Notes on each such trading day; or ​ ● upon the occurrence of specified corporate events described in each Indenture. ​ On or after December 15, 2023, with respect to the 2024 Convertible Notes, and December 15, 2025, with respect to the 2026 Convertible Notes, until the close of business on the second scheduled trading day immediately preceding the applicable maturity date, the holders of the Notes may convert their Notes, in multiples of $1,000 principal amount, regardless of the foregoing conditions. ​ If the Company experiences a fundamental change, as described in the Indentures, prior to the maturity date of the respective Notes, holders of such Notes will, subject to specified conditions, have the right, at their option, to require the Company to repurchase for cash all or a portion of their Notes at a repurchase price equal to 100% of the principal amount of the Notes to be repurchased, plus accrued and unpaid interest, if any, to, but not including, the fundamental change repurchase date. If a make-whole fundamental change, as described in the Indentures, occurs and a holder elects to convert its Notes in connection with such make-whole fundamental change, such holder may be entitled to an increase in the conversion rate as described in the Indentures. ​ The Indentures do not contain any financial covenants or restrict the Company’s ability to repurchase the Company’s securities, pay dividends or make restricted payments in the event of a transaction that substantially increases the Company’s level of indebtedness. The Indentures provide for customary events of default. In the case of an event of default with respect to a series of Notes arising from specified events of bankruptcy or insolvency, all outstanding Notes of such series will become due and payable immediately without further action or notice. If any other event of default with respect to a series of Notes under the relevant Indenture occurs or is continuing, the Trustee or holders of at least 25% in aggregate principal amount of the then outstanding Notes of such series may declare the principal amount of such Notes to be immediately due and payable. ​ In accordance with accounting guidance for debt with conversion and other options, the Company separately accounted for the liability and equity components of the 2024 Convertible Notes and the 2026 Convertible Notes by allocating the proceeds between the liability components and the embedded conversion options, or equity components, due to the Company’s ability to settle the 2024 Convertible Notes and the 2026 Convertible Notes in cash, its Class A Common Stock, or a combination of cash and Class A Common Stock at the option of the Company. The carrying amount of the respective liability components were calculated by measuring the fair value of a similar liability that does not have an associated conversion feature. The respective equity components of the 2024 Convertible Notes and the 2026 Convertible Notes were recognized as a debt discount and represent the difference between the gross proceeds from the issuance of the 2024 Convertible Notes and 2026 Convertible Notes and the fair value of the liability of the 2024 Convertible Notes and 2026 Convertible Notes on their respective dates of issuance. The debt discount is amortized to interest expense using the effective interest method over approximately five ​ The Company’s outstanding balances for the convertible senior notes as of December 31, 2020 and 2019 consisted of the following (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, ​ ​ ​ 2020 ​ 2019 ​ Liability component: ​ ​ ​ ​ ​ ​ Principal: ​ ​ ​ ​ ​ 2022 Convertible Notes ​ $ 120,699 ​ $ 120,699 ​ 2024 Convertible Notes ​ ​ 200,000 ​ ​ 200,000 ​ 2026 Convertible Notes ​ ​ 200,000 ​ ​ 200,000 ​ Less: unamortized debt discount ​ ​ (83,900) ​ ​ (104,700) ​ Less: unamortized debt issuance costs ​ ​ (6,543) ​ ​ (8,005) ​ Net carrying amount ​ $ 430,256 ​ $ 407,994 ​ Equity component: ​ ​ ​ ​ ​ ​ ​ 2022 Convertible Notes ​ ​ 19,807 ​ ​ 19,807 ​ 2024 Convertible Notes ​ ​ 41,152 ​ ​ 41,152 ​ 2026 Convertible Notes ​ ​ 51,350 ​ ​ 51,350 ​ Total equity component ​ $ 112,309 ​ $ 112,309 ​ ​ In connection with the issuance of the 2022 Convertible Notes, the Company incurred approximately $11.7 million of debt issuance costs, which primarily consisted of initial purchasers’ discounts and legal and other professional fees. The Company allocated these costs to the liability and equity components based on the allocation of the proceeds. The portion of these costs allocated to the equity components totaling approximately $4.0 million were recorded as a reduction to additional paid-in capital upon issuance. The portion of these costs allocated to the liability components totaling approximately $7.7 million were recorded as a reduction in the carrying value of the debt on the consolidated balance sheet and are amortized to interest expense using the effective interest method over the expected life of the 2022 Convertible Notes. In connection with the partial repurchase of the 2022 Convertible Notes, the Company recorded a loss on extinguishment of debt of approximately $23.4 million, of which approximately $2.8 million related to the initial debt issuance costs, during the year ended December 31, 2019. The Company determined the expected life of the 2022 Convertible Notes was equal to their seven-year term. The effective interest rate on the liability components of the 2022 Convertible Notes for the period from the date of issuance through June 30, 2019 was 9.34%. From the date of the partial repurchase of the 2022 Convertible Notes in August 2019 through December 31, 2020, the effective interest rate on the liability component of the 2022 Convertible Notes was 9.7%. In connection with the issuance of the 2024 Convertible Notes and the 2026 Convertible Notes, the Company incurred approximately $9.0 million of debt issuance costs, which primarily consisted of initial purchaser’s discounts and legal and other professional fees. The Company allocated these costs to the liability and equity components based on the allocation of the proceeds. The portion of these costs allocated to the equity components totaling approximately $2.1 million were recorded as a reduction to additional paid-in capital. The portion of these costs allocated to the liability components totaling approximately $6.9 million were recorded as a reduction in the carrying value of the debt on the consolidated balance sheet and are amortized to interest expense using the effective interest method over the expected lives of the 2024 Convertible Notes and the 2026 Convertible Notes. ​ The Company determined the expected life of the 2024 Convertible Notes and the 2026 Convertible Notes was equal to their approximately five ​ The following table sets forth total interest expense recognized related to convertible senior notes during the years ended December 31, 2020, 2019, and 2018 (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Year Ended December 31, ​ 2020 2019 ​ 2018 Contractual interest expense ​ $ 7,216 ​ $ 7,361 ​ $ 7,553 Amortization of debt issuance costs ​ ​ 1,462 ​ ​ 1,190 ​ ​ 971 Amortization of debt discount ​ ​ 20,800 ​ ​ 17,683 ​ ​ 15,437 Total interest expense ​ $ 29,478 ​ $ 26,234 ​ $ 23,961 ​ Future minimum payments under the convertible senior notes as of December 31, 2020, are as follows (in thousands): ​ ​ ​ ​ ​ 2021 ​ $ 7,216 2022 ​ ​ 126,557 2023 ​ ​ 4,500 2024 ​ ​ 203,750 2025 ​ ​ 3,000 2026 ​ ​ 201,500 Total future minimum payments under the convertible senior notes ​ 546,523 Less: amounts representing interest ​ ​ (25,824) Less: unamortized debt discount ​ ​ (83,900) Less: unamortized debt issuance costs ​ ​ (6,543) Convertible senior notes balance ​ $ 430,256 ​ Convertible Note Hedge and Note Hedge Warrant Transactions with Respect to 2022 Convertible Notes To minimize the impact of potential dilution to the Company's Class A common stockholders upon conversion of the 2022 Convertible Notes, the Company entered into the Convertible Note Hedges covering 20,249,665 shares of the Company’s Class A Common Stock in connection with the issuance of the 2022 Convertible Notes. The Convertible Note Hedges had an initial exercise price of $16.58 per share, subject to adjustment upon the occurrence of certain corporate events or transactions, and are exercisable if the 2022 Convertible Notes are converted. In connection with the adjustment to the conversion rate of the 2022 Convertible Notes related to the Separation in April 2019, the exercise price of the Convertible Note Hedges was adjusted to $14.51 per share and the number of shares underlying the Convertible Note Hedges was increased to 23,135,435 shares. If upon conversion of the 2022 Convertible Notes, the price of the Company’s Class A Common Stock is above the exercise price of the Convertible Note Hedges, the counterparties are obligated to deliver shares of the Company’s Class A Common Stock and/or cash with an aggregate value approximately equal to the difference between the price of the Company’s Class A Common Stock at the conversion date and the exercise price, multiplied by the number of shares of the Company’s Class A Common Stock related to the Convertible Note Hedge being exercised. Concurrently with entering into the Convertible Note Hedges, the Company sold Note Hedge Warrants to the Convertible Note Hedge counterparties to acquire 20,249,665 shares of the Company’s Class A Common Stock, subject to customary anti-dilution adjustments. The strike price of the Note Hedge Warrants was initially $21.50 per share, subject to adjustment, and such warrants are exercisable over the 150 trading day period beginning on September 15, 2022. In connection with the Separation in April 2019, the exercise price was adjusted to $18.82 per share and the number of shares underlying the Note Hedge Warrants was increased to 23,135,435 shares. The Note Hedge Warrants could have a dilutive effect on the Class A Common Stock to the extent that the market price per share of the Company’s Class A Common Stock exceeds the applicable strike price of such warrants. The Convertible Note Hedges and the Note Hedge Warrants are separate transactions entered into by the Company and are not part of the terms of the 2022 Convertible Notes. Holders of the Convertible Note Hedges and the Note Hedge Warrants do not have any rights with respect to the 2022 Convertible Notes. The Company paid approximately $91.9 million for the Convertible Note Hedges and received approximately $70.8 million for the Note Hedge Warrants, resulting in a net cost to the Company of approximately $21.1 million. In August 2019, concurrently with the repurchase of $215.0 million aggregate principal amount of the 2022 Convertible Notes, the Company terminated the respective portion of the Convertible Note Hedges and Note Hedge Warrants. The Company received approximately $3.2 million of termination payments from the counterparties of the Convertible Note Hedges and Note Hedge Warrants. ​ The Convertible Note Hedges and Note Hedge Warrants are accounted for as derivative assets and liabilities, respectively, in accordance with ASC 815, and are remeasured to fair value at each reporting date (Note 7). Capped Calls with Respect to 2024 Convertible Notes and 2026 Convertible Notes ​ To minimize the impact of potential dilution to the Company’s Class A common stockholders upon conversion of the 2024 Convertible Notes and the 2026 Convertible Notes, the Company entered into separate Capped Calls in connection with the issuance of the 2024 Convertible Notes and the 2026 Convertible Notes. The Company paid the counterparties approximately $25.2 million to enter into the Capped Calls. ​ The Capped Calls have an initial strike price of approximately $13.39 per share, which corresponds to the initial conversion price of the 2024 Convertible Notes and the 2026 Convertible Notes and is subject to anti-dilution adjustments generally similar to those applicable to the 2024 Convertible Notes and the 2026 Convertible Notes. The Capped Calls have a cap price of approximately $17.05 per share, subject to certain adjustments. The Capped Calls cover 29,867,480 shares of Class A Common Stock (subject to anti-dilution and certain other adjustments), which is the same number of shares of Class A Common Stock that initially underlie the 2024 Convertible Notes and the 2026 Convertible Notes. ​ The Capped Calls are expected generally to reduce the potential dilution to the Class A Common Stock upon conversion of the 2024 Convertible Notes and the 2026 Convertible Notes in the event that the market price per share of Class A Common Stock is greater than the strike price of the Capped Calls as adjusted pursuant to the anti-dilution adjustments. If, however, the market price per share of Class A Common Stock exceeds the cap price of the Capped Calls, there would nevertheless be dilution upon conversion of the 2024 Convertible Notes and the 2026 Convertible Notes to the extent that such market price exceeds the cap price of the Capped Calls. ​ The Capped Calls are separate transactions entered into by and between the Company and the Capped Calls counterparties and are not part of the terms of the 2024 Convertible Notes or the 2026 Convertible Notes. Holders of the 2024 Convertible Notes and the 2026 Convertible Notes do not have any rights with respect to the Capped Calls. The Company recorded a reduction to additional paid-in capital of approximately $25.0 million during the year ended December 31, 2019 related to the premium payments for the Capped Calls. Additionally, the Company recorded an approximately $0.2 million reduction to equity related to transaction costs incurred in connection with the Capped Calls during the year ended December 31, 2019. These instruments meet the conditions outlined in ASC 815 to be classified in stockholders’ equity (deficit) and are not subsequently remeasured as long as the conditions for equity classification continue to be met.

Commitments and Contingencies

Commitments and Contingencies	12 Months Ended
	Dec. 31, 2020
Disclosure Text Block
Commitments and Contingencies	12. Commitments and Contingencies Commitments with AbbVie The Company and AbbVie are jointly obligated to make minimum purchases of linaclotide API for the territories covered by the Company’s collaboration with AbbVie for North America. Currently, AbbVie fulfills all such minimum purchase commitments. Under the collaboration agreement with AbbVie for North America, the Company shares all development and commercialization costs related to linaclotide in the U.S. with AbbVie. The actual amounts that the Company pays to AbbVie or that AbbVie pays to the Company will depend on numerous factors outside of the Company’s control, including the success of certain clinical development efforts with respect to linaclotide, the content and timing of decisions made by the regulators, the reimbursement and competitive landscape around linaclotide and the Company’s other product candidates, and other factors. Other Funding Commitments As of December 31, 2020, the Company has on-going studies in various pre-clinical and clinical trial stages. The Company’s most significant clinical trial expenditures are to contract research organizations. These contracts are generally cancellable, with notice, at the Company’s option and do not have any significant cancellation penalties. Guarantees As permitted under Delaware law, the Company indemnifies its directors and certain of its officers for certain events or occurrences while such director or officer is, or was, serving at the Company’s request in such capacity. The maximum potential amount of future payments the Company could be required to make is unlimited; however, the Company has directors’ and officers’ insurance coverage that is intended to limit its exposure and enable it to recover a portion of any future amounts paid. The Company enters into certain agreements with other parties in the ordinary course of business that contain indemnification provisions. These typically include agreements with business partners, contractors, landlords, clinical sites and customers. Under these provisions, the Company generally indemnifies and holds harmless the indemnified party for losses suffered or incurred by the indemnified party as a result of the Company’s activities. These indemnification provisions generally survive termination of the underlying agreements. The maximum potential amount of future payments the Company could be required to make under these indemnification provisions is unlimited. However, to date the Company has not incurred material costs to defend lawsuits or settle claims related to these indemnification provisions. As a result, the estimated fair value of these obligations is minimal. Accordingly, the Company did not have any liabilities recorded for these obligations as of December 31, 2020 and 2019. Litigation From time to time, the Company is involved in various legal proceedings and claims, either asserted or unasserted, which arise in the ordinary course of business. While the outcome of these other claims cannot be predicted with certainty, management does not believe that the outcome of any of these ongoing legal matters, individually and in aggregate, will have a material adverse effect on the Company’s consolidated financial statements. In January 2020, the Company and AbbVie entered into settlement agreements with Sandoz Inc. and Teva Pharmaceuticals, USA resolving patent litigation brought in response to the last outstanding abbreviated new drug applications seeking approval to market generic versions of LINZESS prior to the expiration of the Company’s and AbbVie’s applicable patents. In connection with litigation settlements the Company entered into in 2018, the Company agreed to pay an aggregate of $4.0 million in avoidance of litigation fees and expenses during the year ended December 31, 2018.

Stockholders' Equity

Stockholders' Equity	12 Months Ended
	Dec. 31, 2020
Disclosure Text Block
Stockholders' Equity	13. Stockholders’ Equity Preferred Stock The Company’s preferred stock may be issued from time to time in one or more series, with each such series to consist of such number of shares and to have such terms as adopted by the board of directors. Authority is given to the board of directors to determine and fix such voting powers, full or limited, or no voting powers, and such designations, preferences and relative participating, optional or other special rights, and qualifications, limitation or restrictions thereof, including without limitation, dividend rights, conversion rights, redemption privileges and liquidation preferences. Common Stock The Company has one class of common stock (“Class A Common Stock”). Class A Common Stock is entitled to one vote per share. The Company’s shareholders are entitled to dividends if and when declared by the board of directors.

Employee Stock Benefit Plans

Employee Stock Benefit Plans	12 Months Ended
	Dec. 31, 2020
Disclosure Text Block
Employee Stock Benefit Plans	14. Employee Stock Benefit Plans The Company has several share-based compensation plans under which stock options, RSAs, RSUs, and other share-based awards are available for grant to employees, officers, directors and consultants of the Company. ​ The following table summarizes share-based compensation expense by award type (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Year Ended December 31, ​ 2020 2019 2018 Stock options ​ $ 7,680 ​ $ 12,526 ​ $ 20,478 ​ Time-based restricted stock units ​ ​ 18,624 ​ ​ 15,488 ​ ​ 17,160 ​ Performance-based restricted stock units ​ 2,190 ​ — ​ — ​ Restricted stock awards ​ 1,886 ​ 2,095 ​ 2,330 ​ Employee stock purchase plan ​ 722 ​ 1,115 ​ 1,097 ​ Stock awards ​ 73 ​ 54 ​ 17 ​ ​ ​ $ 31,175 ​ $ 31,278 ​ $ 41,082 ​ ​ The following table summarizes the share-based compensation expense reflected in the consolidated statements of operations (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Years Ended December 31, ​ 2020 2019 2018 Research and development ​ $ 5,569 ​ $ 6,343 ​ $ 11,500 ​ Selling, general and administrative ​ 23,825 ​ 24,281 ​ 27,440 ​ Restructuring expenses ​ ​ 1,781 ​ ​ 654 ​ ​ 2,142 ​ ​ ​ $ 31,175 ​ $ 31,278 ​ $ 41,082 ​ ​ Restructuring expenses include modifications to share-based awards held by employees impacted by the various workforce reductions (Note 18). In April 2019, in connection with the Separation, all outstanding share-based payment awards were modified in accordance with the equity conversion-related provisions of the employee matters agreement with Cyclerion. No share-based compensation expense was recognized in connection with these modifications. Additionally, modifications with respect to the Company’s ESPP were made due to the change in share price as a result of the Separation. As a result of the modification to the ESPP, the Company recorded approximately $0.3 million of share-based compensation expense for the year ended December 31, 2019. ​ In connection with certain other modifications of share-based payment awards for the years ended December 31, 2020 and 2019, the Company recognized an insignificant amount and approximately $3.0 million in share-based compensation expense, respectively. ​ Stock Benefit Plans As of December 31, 2020, the Company has the following active stock benefit plans pursuant to which awards are currently outstanding: the 2019 Equity Incentive Plan (the “2019 Equity Plan”), the Amended and Restated 2010 Employee Stock Purchase Plan (the “2010 Purchase Plan”) and the Amended and Restated 2010 Employee, Director, and Consultant Equity Incentive Plan (the “2010 Equity Plan”). At December 31, 2020, there were 14,357,176 shares available for future grant under the 2019 Equity Plan and the 2010 Purchase Plan. 2019 Equity Plan During 2019, the Company’s stockholders approved the 2019 Equity Plan under which stock options, RSAs, RSUs, and other stock-based awards may be granted to employees, officers, directors, or consultants of the Company. Under the 2019 Equity Plan, 10,000,000 shares of Class A Common Stock were initially reserved for issuance. Awards that are returned to the 2010 Equity Plan as a result of their expiration, cancellation, termination or repurchase are automatically made available for issuance under the 2019 Equity Plan. Awards that expire, cancel, terminate, or are repurchased under the 2019 Equity Plan will no longer be available for future grant. As of December 31, 2020, 9,651,783 shares were available for future grant under the 2019 Equity Plan. ​ 2010 Purchase Plan During 2010, the Company’s stockholders approved the 2010 Purchase Plan, which gives eligible employees the right to purchase shares of common stock at the lower of 85% of the fair market value on the first or last day of an offering period. Each offering period is six months. There were 400,000 shares of common stock initially reserved for issuance pursuant to the 2010 Purchase Plan. The number of shares available for future grant under the 2010 Purchase Plan may be increased on the first day of each fiscal year by an amount equal to the lesser of: (i) 1,000,000 shares, (ii) 1% of the Class A shares of common stock outstanding on the last day of the immediately preceding fiscal year, or (iii) such lesser number of shares as is determined by the board of directors. As of December 31, 2020, there were 4,705,393 shares available for future grant under the 2010 Purchase Plan. 2010 Equity Plan The 2010 Equity Plan provided for the granting of stock options, RSAs, RSUs, and other share-based awards to employees, officers, directors, consultants, or advisors of the Company. At December 31, 2020, there were no shares available for future grant under the 2010 Equity Plan. Restricted Stock Awards RSAs are granted to non-employee members of the board of directors under restricted stock agreements in accordance with the terms of the 2019 Equity Plan and the Company’s non-employee director compensation policy, effective May 2019. Annual restricted stock grants to each non-employee member of the board of directors vest ratably over the period of service from the grant date through the Company’s 2021 annual meeting of stockholders, provided the individual continues to serve on the Company’s board of directors through each vest date. Initial restricted stock grants to new non-employee members of the board of directors vest annually over a three-year period from the date of grant provided the individual continues to serve on the Company’s board of directors through each vest date. A summary of restricted stock activity for the year ended December 31, 2020 is presented below: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Weighted- ​ ​ ​ Average ​ ​ Number of ​ Grant Date ​ ​ Shares ​ Fair Value Unvested as of December 31, 2019 181,648 ​ $ 10.76 ​ Granted 246,500 ​ ​ 10.16 ​ Vested (181,648) ​ ​ 10.46 ​ Forfeited — ​ ​ — ​ Unvested as of December 31, 2020 246,500 ​ $ 10.38 ​ ​ The weighted-average grant date fair value per share of restricted stock awards granted during the years ended December 31, 2020, 2019, and 2018 was $10.16, $10.96, and $18.58, respectively. Amounts relating to restricted stock awards granted prior to the Separation have not been adjusted to reflect the effect of the Separation on the Company’s stock price. Restricted Stock Units RSUs granted under the Company’s equity plans represent the right to receive one share of the Company’s Class A Common Stock pursuant to the terms of the applicable award agreement. Shares of the Company’s Class A Common Stock are delivered to the employee upon vesting, subject to payment of applicable withholding taxes. Time-based RSUs Time-based RSUs generally vest over a two A summary of time-based RSU activity for the year ended December 31, 2020 is as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Weighted- ​ ​ ​ ​ ​ Average ​ ​ ​ Number ​ Grant Date ​ ​ of RSUs Fair Value Outstanding as of December 31, 2019 3,207,089 ​ $ 12.33 ​ Granted ​ 2,708,200 ​ ​ 11.59 ​ Vested and released ​ (965,625) ​ ​ 12.37 ​ Forfeited ​ (779,038) ​ ​ 11.96 ​ Outstanding as of December 31, 2020 4,170,626 ​ $ 11.90 ​ ​ The weighted-average grant date fair value per share of time-based RSUs granted during the years ended December 31, 2020, 2019, and 2018 was $11.59, $12.11, and $15.63, respectively. Amounts relating to time-based RSUs granted prior to the Separation have not been adjusted to reflect the effect of the Separation on the Company’s stock price. ​ Performance-based RSUs ​ Performance-based RSUs (“PSUs”) were granted to certain executives in 2020. PSUs vest upon the achievement of specified performance criteria over a two ​ The fair value of Pipeline PSUs and Profitability PSUs is based on the market value of the Company's Class A Common Stock on the date of grant. The Relative TSR PSUs are valued using the Monte Carlo simulation method on the date of grant. The weighted average assumptions used to estimate the fair value of Relative TSR PSUs were as follows for the year ended December 31, 2020: ​ ​ ​ ​ ​ ​ ​ Year Ended December 31, ​ 2020 ​ ​ ​ Fair value of common stock $ 11.78 ​ Expected volatility 53.3 % Expected term (in years) 2.8 ​ Risk-free interest rate 1.0 % Expected dividend yield — % ​ ​ A summary of PSU activity for the year ended December 31, 2020 is as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Weighted- ​ ​ ​ ​ ​ Average ​ ​ ​ Number ​ Grant Date ​ ​ of RSUs Fair Value (1) Outstanding as of December 31, 2019 — ​ $ — ​ Granted ​ 586,157 ​ ​ 12.48 ​ Vested and released ​ — ​ ​ — ​ Forfeited ​ — ​ ​ — ​ Outstanding as of December 31, 2020 586,157 ​ $ 12.48 ​ ​ No PSUs were granted prior to the year ended December 31, 2020. ​ Stock Options ​ Stock options granted under the Company’s equity plans represent the right to purchase one share of the Company’s Class A Common Stock pursuant to the terms of the applicable award agreement. Shares of the Company's Class A Common Stock are delivered to the employee upon exercise, subject to payment of applicable withholding taxes. ​ As of April 2020, the Company no longer grants stock options. Stock options previously granted under the Company’s equity plans generally have a ten-year term and vest over a period of four years, provided the individual continues to serve at the Company through the vesting dates. Options granted under all equity plans are exercisable at a price per share not less than the fair market value of the underlying common stock on the date of grant. The estimated fair value of options, including the effect of estimated forfeitures, is recognized over the requisite service period, which is typically the vesting period of each option. ​ The weighted average assumptions used to estimate the fair value of the stock options using the Black-Scholes option-pricing model were as follows for the years ended December 31, 2020, 2019, and 2018: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Years Ended December 31, ​ ​ ​ 2020 ​ 2019 ​ 2018 ​ Expected volatility ​ 46.6 % 46.3 % 43.7 % Expected term (in years) ​ 6.1 ​ 6.1 ​ 6.0 ​ Risk-free interest rate ​ 1.5 % 2.5 % 2.7 % Expected dividend yield ​ — % — % — % ​ Expected volatility is based on the historical volatility of the Company’s Class A Common Stock. The Company estimates the expected term using historical data. The risk-free interest rate used for each grant is based on a zero-coupon U.S. Treasury instrument with a remaining term similar to the expected term of the share-based award. The Company has not paid and does not anticipate paying cash dividends on its shares of common stock in the foreseeable future; therefore, the expected dividend yield is assumed to be zero. The weighted-average grant date fair value per share of options granted during the years ended December 31, 2020, 2019, and 2018 was $5.89, $6.10, and $6.81, respectively. Amounts relating to stock options granted prior to the Separation have not been adjusted to reflect the effect of the Separation on the Company’s stock price. The Company historically granted to certain employees performance-based options to purchase shares of common stock. These options are subject to performance-based milestone vesting. During the years ended December 31, 2020 and 2019, there were no shares that vested as a result of performance milestone achievements. The Company recorded no share-based compensation expense related to these performance-based options during each of the years ended December 31, 2020, 2019, and 2018. The following table summarizes stock option activity under the Company’s share-based compensation plans, including performance-based options: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Weighted- ​ Weighted- ​ ​ ​ ​ ​ Number of ​ Average ​ Average ​ Aggregate ​ ​ Stock ​ Exercise ​ Contractual ​ Intrinsic ​ ​ Options ​ Price (1) ​ Life ​ Value ​ ​ ​ ​ ​ ​ ​ (in years) ​ (in thousands) Outstanding at December 31, 2019 17,194,239 ​ $ 12.13 ​ 5.11 ​ $ 25,226 ​ Granted 55,000 ​ ​ 12.84 ​ — ​ ​ — ​ Exercised (1,735,081) ​ ​ 10.21 ​ — ​ ​ — ​ Cancelled (2,054,487) ​ ​ 13.00 ​ — ​ ​ — ​ Outstanding at December 31, 2020 13,459,671 ​ ​ 12.25 ​ 4.27 ​ ​ 5,613 ​ Vested or expected to vest at December 31, 2020 13,280,456 ​ ​ 12.26 ​ 4.23 ​ ​ 5,575 ​ Exercisable at December 31, 2020 11,963,812 ​ ​ 12.26 ​ 3.90 ​ ​ 5,371 ​ ​ (1) Exercise prices relating to stock options granted prior to the Separation have not been adjusted to reflect the effect of the Separation on the stock options. ​ The total intrinsic value of options exercised during the years ended December 31, 2020, 2019, and 2018 was approximately $3.5 million, approximately $5.1 million, and approximately $20.1 million, respectively. The intrinsic value was calculated as the difference between the fair value of the Company’s Class A Common Stock and the exercise price of the option issued. The following table sets forth the Company's unrecognized share-based compensation expense, net of estimated forfeitures, as of December 31, 2020, by type of award and the weighted-average period over which that expense is expected to be recognized: ​ ​ ​ ​ ​ ​ ​ ​ ​ Unrecognized Weighted-Average ​ ​ Expense, Net ​ Remaining ​ ​ of Estimated ​ Recognition ​ ​ ​ Forfeitures ​ Period ​ ​ (in thousands) ​ (in years) Type of award: ​ ​ ​ ​ ​ ​ Stock options with time-based vesting ​ $ 6,557 ​ 1.84 ​ Restricted stock awards ​ ​ 1,473 ​ 0.92 ​ Time-based restricted stock units ​ ​ 26,934 ​ 2.22 ​ Performance-based restricted stock units ​ ​ 3,291 ​ 1.70 ​ Stock options with time-based and performance-based vesting (1) ​ ​ 88 ​ — ​ (1) The weighted-average remaining recognition period cannot be determined for performance-based or time-accelerated options due to the nature of such awards, as detailed above. ​ The total unrecognized share-based compensation cost will be adjusted for future changes in estimated forfeitures.

Income Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2020
Disclosure Text Block
Income Taxes	15. Income Taxes During the year ended December 31, 2020, the Company recorded approximately $2.7 million in income tax expense related to state income tax, which primarily resulted from a change in California tax which temporarily disallows the use of net operating losses to offset taxable income. The Company did not record a provision for federal income taxes for the period ended December 31, 2020, as it offset taxable income with federal net operating losses and continues to record a full valuation allowance against net deferred tax assets. The Company did not record a provision for federal, state, or foreign income taxes for the period ended December 31, 2019 and 2018, respectively, because the Company incurred a tax loss during these years and offset the benefit of these tax losses with valuation allowance. The Company has not recorded a foreign tax provision as it has had cumulative net operating losses outside of the United States since inception. On March 27, 2020. the Coronavirus Aid, Relief, and Economic Security (“CARES”) Act was enacted and signed into law. The Company benefitted from certain provisions of the CARES Act, specifically, the increase in allowable business interest deduction from 30% of adjusted taxable income to 50% of adjusted taxable income, which allowed the Company to take additional interest deductions for the period ended December 31, 2020. Additionally, the Company was able to claim 100% bonus depreciation on leasehold improvements incurred in the period ended December 31, 2019 and 2020. A reconciliation of income taxes computed using the U.S. federal statutory rate of 21% to that reflected in the consolidated statements of operations are as follows (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Year Ended December 31, ​ 2020 2019 2018 Income tax benefit using U.S. federal statutory rate ​ $ 22,861 ​ $ 4,517 ​ $ (59,297) ​ Permanent differences ​ 74 ​ 65 ​ 218 ​ State income taxes, net of federal benefit ​ 7,565 ​ (1,902) ​ (17,121) ​ Disallowed Separation related costs ​ ​ — ​ ​ 4,658 ​ ​ — ​ Executive compensation - Section 162(m) ​ ​ 1,718 ​ ​ 662 ​ ​ 8 ​ Meals and entertainment ​ ​ 395 ​ ​ 495 ​ ​ 995 ​ Non-deductible share-based compensation ​ (144) ​ (1,202) ​ (494) ​ Excess tax benefits ​ ​ 5,132 ​ ​ 3,324 ​ ​ (1,223) ​ Fair market valuation of Note Hedge Warrants and Convertible Note Hedges ​ ​ 1,680 ​ ​ (290) ​ ​ 2,367 ​ Tax credits ​ (3,149) ​ (4,374) ​ (7,863) ​ Expiring net operating losses and tax credits ​ 1,991 ​ 3,764 ​ 250 ​ Effect of change in state tax rate on deferred tax assets and deferred tax liabilities ​ (208) ​ (2,563) ​ 1,476 ​ Change in the valuation allowance ​ (35,230) ​ (7,154) ​ 80,684 ​ Income tax expense ​ $ 2,685 ​ $ — ​ $ — ​ ​ Deferred tax assets and liabilities were determined based on the difference between financial statement and tax bases using enacted tax rates in effect for the year in which the differences are expected to reverse. The components of the Company’s deferred tax assets and liabilities are as follows (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, ​ 2020 2019 Deferred tax assets: ​ ​ ​ ​ ​ ​ ​ Net operating loss carryforwards ​ $ 234,772 ​ $ 265,494 ​ Tax credit carryforwards ​ 60,607 ​ 59,892 ​ Capitalized research and development ​ 7,498 ​ 9,952 ​ Share-based compensation ​ ​ 21,848 ​ ​ 24,401 ​ Basis difference on collaboration agreement for North America with AbbVie ​ ​ 62,629 ​ ​ 48,594 ​ Accruals and reserves ​ ​ 6,114 ​ ​ 6,415 ​ Basis difference on 2022 Convertible Notes ​ ​ 6,183 ​ ​ 4,322 ​ Interest expense ​ ​ 3,386 ​ ​ 22,020 ​ Operating lease liability ​ ​ 6,504 ​ ​ 6,421 ​ Other ​ 5,049 ​ 5,295 ​ Total deferred tax assets ​ 414,590 ​ 452,806 ​ Deferred tax liabilities: ​ ​ ​ ​ ​ ​ ​ Basis difference on 2024 Convertible Notes ​ ​ (5,951) ​ ​ (7,381) ​ Basis difference on 2026 Convertible Notes ​ ​ (9,022) ​ ​ (10,276) ​ Operating lease right-of-use assets ​ ​ (4,603) ​ ​ (4,905) ​ Total deferred tax liabilities ​ ​ (19,576) ​ ​ (22,562) ​ Net deferred tax asset ​ ​ 395,014 ​ ​ 430,244 ​ Valuation allowance ​ (395,014) ​ (430,244) ​ Net deferred tax asset ​ $ — ​ $ — ​ ​ On a periodic basis, the Company reassesses the valuation allowance on its deferred income tax assets weighing positive and negative evidence to assess the recoverability of the deferred tax assets. Management evaluated the positive evidence, including income during the year ended December 31, 2020, and negative evidence, including its cumulative losses in recent years and its plan to build its innovative GI pipeline through potential acquisition or in-licensing externally development products, and concluded that it is more likely than not that the Company will not realize the benefit of its deferred tax assets for the year ended December 31, 2020. Accordingly, the net deferred tax assets have been fully offset by a valuation allowance as of December 31, 2020 and 2019. Management re-evaluates the positive and negative evidence on a quarterly basis. Based on the Company’s financial performance and its future projections, it may record a reversal of all, or a portion of the valuation allowance associated with its deferred tax assets in future periods. However, any such change is subject to actual performance and other considerations that may present positive or negative evidence at the time of the assessment. The Company’s total deferred tax asset balance subject to a valuation allowance was $395.0 million and approximately $430.2 million as of December 31, 2020 and 2019, respectively. The valuation allowance decreased approximately $35.2 million during the year ended December 31, 2020 primarily due to the Company’s offsetting taxable income with previously disallowed interest expense and net operating losses, partially offset by an increase in deferred tax asset for the basis difference of the collaboration agreement for North America with AbbVie. The valuation allowance decreased approximately $29.1 million during the year ended December 31, 2019 primarily due to establishment of a deferred tax liability for a basis difference in the 2024 Convertible Notes and 2026 Convertible Notes, partially offset by an increase in the deferred tax asset for temporarily disallowed interest expense. Subject to the limitations described below, at December 31, 2020, the Company had federal net operating loss carryforwards of approximately $1.1 billion of which approximately $1.0 billion is subject to an expiration between 2021 and 2037 and $0.1 billion may be carried forward indefinitely. As of December 31, 2020, the Company had state net operating loss carryforwards of approximately $0.9 billion to offset future state taxable income, which is subject to expiration between 2021 and 2039. The Company also had tax credit carryforwards of approximately $65.3 million as of December 31, 2020 to offset future federal and state income taxes, which is subject to expiration at various times through 2040. Utilization of net operating loss carryforwards and research and development credit carryforwards may be subject to a substantial annual limitation due to ownership change limitations that could occur in the future in accordance with Section 382 of the Internal Revenue Code of 1986 (“IRC Section 382”) and with Section 383 of the Internal Revenue Code of 1986, as well as similar state provisions. These ownership changes may limit the amount of net operating loss carryforwards and research and development credit carryforwards that can be utilized annually to offset future taxable income and taxes, respectively. In general, an ownership change, as defined by IRC Section 382, results from transactions increasing the ownership of certain stockholders or public groups in the stock of a corporation by more than 50 percentage points over a three-year period. The following table summarizes the changes in the Company’s unrecognized income tax benefits for the years ended December 31, 2020, 2019, and 2018 (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Year Ended December 31, ​ ​ ​ 2020 ​ 2019 ​ 2018 ​ Balance at the beginning of the period ​ $ 53,099 ​ $ 38,551 ​ $ 24,078 ​ Increases based on tax positions related to the current period ​ ​ 66,687 ​ ​ 51,699 ​ ​ 38,551 ​ Increases for tax positions related to prior periods ​ ​ — ​ ​ 1,400 ​ ​ — ​ Decreases for tax positions in prior periods ​ ​ (51,699) ​ ​ (38,551) ​ ​ (24,078) ​ Balance at the end of the period ​ $ 68,087 ​ $ 53,099 ​ $ 38,551 ​ ​ The Company had gross unrecognized tax benefits of approximately $68.1 million, approximately $53.1 million, and approximately $38.6 million as of December 31, 2020, 2019 and 2018 . total unrecognized tax benefits at December 31, 2020, approximately $0.8 million would, if recognized, affect the Company’s effective tax rate, and the remaining amount would not affect the Company’s effective tax rate due to a valuation allowance against the Company’s net deferred tax assets. A reserve for uncertain tax positions of approximately $0.8 million is recorded in other liabilities on the Company’s consolidated balance sheet as of December 31, 2020. The Company will recognize interest and penalties, if any, related to uncertain tax positions in income tax expense. As of December 31, 2020, no interest or penalties have been accrued. The statute of limitations for assessment by the Internal Revenue Service (“IRS”) and state tax authorities is open for tax years ended December 31, 2017 through the present, although net operating losses generated from years prior to 2017 could be subject to examination and adjustments to the extent utilized in future years. There are currently no federal or state income tax audits in progress.

Defined Contribution Plan

Defined Contribution Plan	12 Months Ended
	Dec. 31, 2020
Disclosure Text Block
Defined Contribution Plan	16. Defined Contribution Plan The Ironwood Pharmaceuticals, Inc. 401(k) Savings Plan is a defined contribution plan in the form of a qualified 401(k) plan in which substantially all employees are eligible to participate upon employment. Subject to certain IRS limits, eligible employees may elect to contribute from 1% to 100% of their compensation. Company contributions to the plan are at the sole discretion of the Company’s board of directors. Currently, the Company provides a matching contribution of 75% of the employee’s contributions, up to $6,000 annually. During the years ended December 31, 2020, 2019, and 2018, the Company recorded approximately $1.8 million, approximately $2.2 million, and approximately $3.2 million of expense related to its 401(k) company match, respectively.

Related Party Transactions

Related Party Transactions	12 Months Ended
	Dec. 31, 2020
Disclosure Text Block
Related Party Transactions	17. Related Party Transactions The Company previously reflected amounts due to and due from Allergan prior to its acquisition by AbbVie as related party accounts payable and related party accounts receivable, respectively. Following the acquisition of Allergan by AbbVie, the Company determined that AbbVie is not a related party to the Company. As such, only historical amounts paid to and received from Allergan (prior to its acquisition by AbbVie) are considered related party accounts payable and related party accounts receivable, respectively. Balances of related party accounts payable and related party accounts receivable, respectively, were reported net of any balances due to or from the related party. ​ In connection with the Separation, the Company executed certain contracts with Cyclerion, whose President and Chief Scientific Officer at the time of the Separation became a member of the Company’s Board of Directors in April 2019 (Note 3). As of December 31, 2020, Cyclerion was no longer considered a related party. ​

Workforce Reduction and Restruc

Workforce Reduction and Restructuring	12 Months Ended
	Dec. 31, 2020
Disclosure Text Block
Workforce Reduction and Restructuring	18. Workforce Reductions and Restructuring During the years ended December 31, 2020, 2019, and 2018 the Company recorded approximately $15.4 ​ In January 2018, the Company commenced an initiative to evaluate the optimal mix of investments for the lesinurad franchise. As part of this effort, the Company reduced its field-based workforce by approximately 60 employees, primarily consisting of field-based sales representatives that promoted DUZALLO or ZURAMPIC in the first position. During the three months ended March 31, 2018, the Company substantially completed this reduction in field-based workforce and recorded approximately $2.4 million of severance, benefits and related costs as restructuring expenses during the year ended December 31, 2018 related to this reduction in workforce. ​ In June 2018, the Company determined the initial organizational designs of the two new businesses, including employees’ roles and responsibilities, in connection with the Separation. As part of this process, the Company initiated a reduction in its headquarters-based workforce by approximately 40 employees and substantially completed the reduction in its workforce during the year ended December 31, 2018. During the year ended December 31, 2018, the Company recorded approximately $4.0 million of severance, benefits and related costs as restructuring expenses related to this reduction in workforce. ​ In August 2018, the Company initiated a reduction in its workforce by approximately 100 employees, primarily consisting of field-based sales representatives in connection with the termination of the Lesinurad License and substantially completed the reduction in its workforce and recorded associated costs during the year ended December 31, 2018. During the years ended December 31, 2020 and 2019, the Company recorded an insignificant amount of adjustments to restructuring costs related to this workforce reduction. During the year ended December 31, 2018, the Company recorded approximately $8.3 million of restructuring expenses, including approximately $5.4 million of severance, benefits and related costs and approximately $2.9 million of contract-related costs, including the write-down of certain prepaid assets and deposits, in connection with this reduction in workforce. ​ In February 2019, following further analysis of the Company’s strategy and core business needs, and in an effort to further strengthen the operational efficiency of the organization, the Company commenced a reduction in workforce by approximately 35 employees, primarily based in the home office and substantially completed the reduction in its workforce and recorded associated costs during the year ended December 31, 2019. During the year ended December 31, 2019, the Company recorded approximately $3.7 million of severance, benefits and related costs as restructuring expenses related to this reduction in workforce. ​ In September 2020, the Company announced that one of its two identical Phase III trials evaluating IW-3718 in refractory GERD did not meet certain criteria, including the study’s primary endpoint of achieving a statistically significant improvement in heartburn severity. Based on these findings, the Company is discontinuing development of IW-3718. In connection with this decision, the Company reduced its workforce by approximately 100 full-time employees. This workforce reduction affected both field-based and home-office employees, including the relevant general and administrative support functions. The Company substantially completed the reduction in its workforce in the fourth quarter of 2020. The Company incurred approximately $15.5 million during the year ended December 31, 2020 in restructuring expenses, primarily for severance, benefits and related costs related to this reduction in force. Restructuring expenses during the year ended December 31, 2020 also included approximately $1.2 million related to the impairment of certain fixed assets as a result of the Company’s decision to discontinue IW-3718 development. ​ The following table summarizes the accrued liabilities activity recorded in connection with the reductions in workforce and related restructuring activities during the year ended December 31, 2020 (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Amounts ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Amounts ​ ​ Accrued at ​ ​ ​ ​ ​ ​ ​ ​ ​ Accrued at ​ ​ December 31, 2019 Charges ​ Amount Paid ​ Adjustments ​ December 31, 2020 ​ Employee severance, benefits and related costs ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ February 2019 Reduction ​ 75 ​ ​ — ​ ​ (75) ​ ​ — ​ ​ — ​ September 2020 Reduction ​ — ​ ​ 11,563 ​ ​ (661) ​ ​ — ​ ​ 10,902 ​ Total $ 75 ​ $ 11,563 ​ $ (736) ​ $ — ​ $ 10,902 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Contract related costs ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ August 2018 Reduction $ 104 ​ $ — ​ $ — ​ $ (104) ​ $ — ​ September 2020 Reduction ​ — ​ ​ 108 ​ ​ (103) ​ ​ — ​ ​ 5 ​ Total $ 104 ​ $ 108 ​ $ (103) ​ $ (104) ​ $ 5 ​ ​ The following table summarizes the accrued liabilities activity recorded in connection with the reductions in workforce and related restructuring activities during the year ended December 31, 2019 (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Amounts ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Amounts ​ ​ Accrued at ​ ​ ​ ​ ​ ​ ​ ​ ​ Accrued at ​ ​ December 31, 2018 Charges ​ Amount Paid ​ Adjustments ​ December 31, 2019 ​ Employee severance, benefits and related costs ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ June 2018 Reduction $ 696 ​ $ 16 ​ $ (689) ​ $ (23) ​ $ — ​ August 2018 Reduction ​ 1,756 ​ ​ — ​ ​ (1,708) ​ ​ (48) ​ ​ — ​ February 2019 Reduction ​ — ​ ​ 3,182 ​ ​ (2,968) ​ ​ (139) ​ ​ 75 ​ Total $ 2,452 ​ $ 3,198 ​ $ (5,365) ​ $ (210) ​ $ 75 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Contract related costs ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ August 2018 Reduction $ 433 ​ $ — ​ $ (287) ​ $ (42) ​ $ 104 ​ Total $ 433 ​ $ — ​ $ (287) ​ $ (42) ​ $ 104 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​

Selected Quarterly Financial Da

Selected Quarterly Financial Data (Unaudited)	12 Months Ended
	Dec. 31, 2018
Disclosure Text Block
Selected Quarterly Financial Data (Unaudited)	19. Selected Quarterly Financial Data (Unaudited) The following table contains quarterly financial information for the years ended December 31, 2020 and 2019. The Company believes that the following information reflects all normal recurring adjustments necessary for a fair presentation of the information for the periods presented. The operating results for any quarter are not necessarily indicative of results for any future period. ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ First ​ Second ​ Third ​ Fourth ​ Total ​ ​ Quarter ​ Quarter ​ Quarter ​ Quarter ​ Year ​ ​ (in thousands, except per share data) 2020 ​ ​ ​ ​ ​ Total revenues (1) ​ $ 79,943 ​ $ 89,432 ​ $ 103,468 ​ $ 116,680 ​ $ 389,523 ​ Total cost and expenses (2) ​ 66,716 ​ 56,719 ​ 57,852 ​ 65,296 ​ 246,583 ​ Other expense, net (3) ​ (9,882) ​ (7,509) ​ (9,804) ​ (6,884) ​ (34,079) ​ Net income and comprehensive income ​ 3,345 ​ 25,204 ​ 34,423 ​ 43,204 ​ 106,176 ​ Net income per share—basic ​ ​ 0.02 ​ ​ 0.16 ​ ​ 0.22 ​ ​ 0.27 ​ ​ 0.67 ​ Net income per share—diluted ​ ​ 0.02 ​ ​ 0.16 ​ ​ 0.21 ​ ​ 0.27 ​ ​ 0.66 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ First ​ Second ​ Third ​ Fourth ​ Total ​ ​ Quarter ​ Quarter ​ Quarter ​ Quarter ​ Year ​ ​ (in thousands, except per share data) 2019 ​ ​ ​ ​ ​ Total revenues (4) ​ $ 68,730 ​ $ 102,215 ​ $ 131,167 ​ $ 126,301 ​ $ 428,413 ​ Total cost and expenses (5) ​ 85,663 ​ 80,638 ​ 65,280 ​ 76,709 ​ 308,290 ​ Other expense, net (6) ​ (4,912) ​ (9,294) ​ (45,239) ​ (1,735) ​ (61,180) ​ Net (loss) income from continuing operations ​ ​ (21,846) ​ ​ 12,283 ​ ​ 20,648 ​ ​ 47,858 ​ 58,943 ​ Net loss from discontinued operations (7) ​ ​ (37,438) ​ ​ — ​ ​ — ​ ​ — ​ (37,438) ​ Net income (loss) and comprehensive income (loss) ​ (59,284) ​ 12,283 ​ 20,648 ​ 47,858 ​ 21,505 ​ Income per share from continuing operations, net of income taxes—basic ​ $ (0.14) ​ $ 0.08 ​ $ 0.13 ​ $ 0.31 ​ $ 0.38 ​ Income per share from continuing operations, net of income taxes—diluted ​ ​ (0.14) ​ ​ 0.08 ​ ​ 0.13 ​ ​ 0.30 ​ ​ 0.38 ​ Net loss per share from discontinued operations—basic and diluted ​ ​ (0.24) ​ ​ — ​ ​ — ​ ​ — ​ ​ (0.24) ​ Net income (loss) per share—basic ​ ​ (0.38) ​ ​ 0.08 ​ ​ 0.13 ​ ​ 0.31 ​ ​ 0.14 ​ Net income (loss) per share—diluted ​ ​ (0.38) ​ ​ 0.08 ​ ​ 0.13 ​ ​ 0.30 ​ ​ 0.14 ​ (1) Total revenues includes approximately $8.0 million of revenue from sales of linaclotide API to the Company’s linaclotide partners for the year ended December 31, 2020. (2) Total costs and expenses includes approximately $15.4 million in restructuring expenses for the year ended December 31, 2020. (3) Other expense, net includes approximately $6.1 million loss on fair value remeasurement of derivatives for the year ended December 31, 2020. (4) Total revenues includes approximately $48.8 million of revenue from sales of linaclotide API to the Company’s linaclotide partners, primarily driven by the commercialization of linaclotide in Japan for the year ended December 31, 2019, as well as approximately $32.4 million related to the non-contingent payments from the Amended AstraZeneca Agreement and a $10.0 million upfront fee from the Amended Astellas License Agreement, both executed during the third quarter of 2019. (5) Total costs and expenses includes approximately $3.6 million in restructuring expenses for the year ended December 31, 2019, as well as approximately $3.2 million related to the gain on lease modification in April 2019. (6) Other expense, net includes approximately $31.0 million in loss on extinguishment of debt related to the partial repurchase of the 2022 Convertible Notes and the redemption of the 2026 Notes, and approximately $3.0 million gain on fair value remeasurement of derivatives for the year ended December 31, 2019. (7) During the year ended December 31, 2019, the Company completed the Separation. Certain amounts related to Cyclerion have been reclassified as discontinued operations for the year ended December 31, 2019.

Subsequent Events

Subsequent Events	12 Months Ended
	Dec. 31, 2020
Disclosure Text Block
Subsequent Events	20. Subsequent Events ​ On February 4, 2021, Mark Mallon notified the Company that he is resigning from his position as Chief Executive Officer of the Company and a member of the Company’s board of directors, in each case effective March 12, 2021 (the “Transition Date”). Upon the Transition Date, Thomas McCourt, who is the President of the Company, also will become the Company’s interim Chief Executive Officer. Mr. Mallon’s resignation is not due to any disagreement with the Company on any matter relating to the Company’s operations, policies, or practices. ​ ​ ​ ​

Summary of Significant Accoun_2

Summary of Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2020
Policy Text Blocks
Principles of Consolidation	Principles of Consolidation The accompanying consolidated financial statements include the accounts of Ironwood and its wholly-owned subsidiaries, as of December 31, 2020, Ironwood Pharmaceuticals Securities Corporation and Ironwood Pharmaceuticals GmbH. Cyclerion was a wholly-owned subsidiary until it became an independent publicly-traded company on April 1, 2019. All intercompany transactions and balances are eliminated in consolidation.
Segment Information	Segment Information Operating segments are components of an enterprise for which separate financial information is available and is evaluated regularly by the Company’s chief operating decision-maker in deciding how to allocate resources and in assessing performance. The Company currently operates in one reportable business segment—human therapeutics.
Reclassifications	Reclassifications ​ Certain prior period financial statement items have been reclassified to conform to current period presentation.
Discontinued Operations	Discontinued Operations ​ The Company determined that its sGC business, which was disposed on April 1, 2019, met the criteria for classification as a discontinued operation in accordance with Accounting Standards Codification (“ASC”) Subtopic 205-20, Discontinued Operations Cyclerion Separation
Use of Estimates	Use of Estimates The preparation of consolidated financial statements in accordance with U.S. generally accepted accounting principles requires the Company’s management to make estimates and judgments that may 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 amounts of revenues and expenses during the reported periods. On an ongoing basis, the Company’s management evaluates its estimates, judgments and methodologies. Significant estimates and assumptions in the consolidated financial statements include those related to revenue recognition; accounts receivable; inventory valuation and related reserves; useful lives of long-lived assets, impairment of long-lived assets, including its acquired intangible assets and goodwill; valuation procedures for right-of-use assets and operating lease liabilities; valuation procedures for the issuance and repurchase of convertible notes; balance sheet classification of convertible notes; valuation of assets and liabilities held for disposition and losses related to discontinued operations; fair value of derivatives; income taxes, including the valuation allowance for deferred tax assets; research and development expenses; contingencies and share-based compensation. The Company bases its estimates on historical experience and on various other assumptions that are believed to be reasonable, the results of which form the basis for making judgments about the carrying values of assets and liabilities. Actual results may differ materially from these estimates under different assumptions or conditions. Changes in estimates are reflected in reported results in the period in which they become known.
Cash and Cash Equivalents	Cash and Cash Equivalents The Company considers all highly liquid investment instruments with a remaining maturity when purchased of three months or less to be cash equivalents. Investments qualifying as cash equivalents primarily consist of money market funds, U.S. government-sponsored securities, and repurchase agreements. The carrying amount of cash equivalents approximates fair value. The amount of cash equivalents included in cash and cash equivalents was approximately $349.0 million and approximately $177.0 million at December 31, 2020 and 2019, respectively.
Restricted Cash	Restricted Cash The Company is contingently liable under unused letters of credit with a bank, related to the Company’s facility lease and vehicle lease agreements, in the amount of approximately $2.2 million as of December 31, 2020 and 2019. The Company records as restricted cash the collateral used to secure these letters of credit. The amount of restricted cash included in current assets and non-current assets was approximately $1.7 million and $0.5 million at December 31, 2020, respectively. The amount of restricted cash in current assets and non-current assets was approximately $1.2 million and $1.0 million at December 31, 2019, respectively.
Concentrations of Suppliers	Concentrations of Suppliers The Company relies on its collaboration partners and their suppliers to manufacture linaclotide API, linaclotide finished drug product, and finished goods. If any of the Company’s collaboration partners and their suppliers were to limit or terminate production or otherwise fail to meet the quality or delivery requirements needed to satisfy the supply commitments, the process of locating and qualifying alternate sources could require up to several months, during which time production could be delayed. Such delays could have a material adverse effect on the Company’s business, financial position and results of operations.
Accounts Receivable and Related Valuation Account	Accounts Receivable and Related Valuation Account The Company makes judgments as to its ability to collect outstanding receivables and provides an allowance for credit losses when collection becomes doubtful. Provisions are made based upon a specific review of all significant outstanding invoices and the overall quality and age of those invoices not specifically reviewed. The Company’s receivables relate primarily to amounts reimbursed under its collaboration, license and co-promotion agreements. The Company believes that credit risks associated with these partners are not significant. The Company reviews the need for an allowance for credit losses for its receivables based on various factors including payment history and historical bad debt experience. The Company had no allowance for credit losses as of December 31, 2020 or 2019.
Concentrations of Credit Risk	Concentrations of Credit Risk Financial instruments that subject the Company to credit risk primarily consist of cash and cash equivalents, restricted cash, and accounts receivable. The Company maintains its cash and cash equivalent balances with high-quality financial institutions and the Company believes that such funds are subject to minimal credit risk. The Company has adopted an investment policy which limits the amounts the Company may invest in certain types of investments, and requires all investments held by the Company to be at least AA- rated, thereby reducing credit risk exposure. Accounts receivable primarily consist of amounts due under the linaclotide collaboration agreement with AbbVie for North America (Note 6). The Company does not obtain collateral for its accounts receivable. The Company previously reflected amounts due from Allergan, net of amounts payable to Allergan, prior to its acquisition by AbbVie as related party accounts receivable, net. Following the acquisition of Allergan by AbbVie, the Company determined that AbbVie is not a related party to the Company (Note 17). The percentages of revenue recognized from significant collaborative partners of the Company in the years ended December 31, 2020, 2019 and 2018 as well as the account receivable balances, net of any payables due, at December 31, 2020 and 2019 are included in the following table: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Accounts ​ Revenue ​ ​ December 31, ​ Year Ended December 31, ​ 2020 2019 2020 2019 2018 Collaborative Partner: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ AbbVie (North America and Europe) 76 % 90 % 96 % 78 % 77 % Astellas (Japan) 1 % 8 % 1 % 13 % 20 % ​ For the years ended December 31, 2020, 2019 and 2018, no additional customers accounted for more than 10% of the Company’s revenue.
Property and Equipment	Property and Equipment ​ Property and equipment, including leasehold improvements, are recorded at cost, and are depreciated when placed into service using the straight-line method based on their estimated useful lives as follows: ​ ​ ​ ​ ​ ​ Estimated Useful Life Asset Description (In Years) Laboratory equipment 5 ​ Computer and office equipment 3 ​ Furniture and fixtures 7 ​ Software 3 ​ ​ Included in property and equipment are certain costs of software obtained for internal use. Costs incurred during the preliminary project stage are expensed as incurred, while costs incurred during the application development stage are capitalized and amortized over the estimated useful life of the software. The Company also capitalizes costs related to specific upgrades and enhancements when it is probable the expenditures will result in additional functionality. Maintenance and training costs related to software obtained for internal use are expensed as incurred. Leasehold improvements are amortized over the shorter of the estimated useful life of the asset or the lease term. Costs for capital assets not yet placed into service have been capitalized as construction in process, and will be depreciated in accordance with the above guidelines once placed into service. Maintenance and repair costs are expensed as incurred.
Finite Lived Intangible Assets	Finite Lived Intangible Assets The Company records the fair value of purchased intangible assets with finite useful lives as of the transaction date of a business combination. Purchased intangible assets with finite useful lives are amortized to their estimated residual values over their estimated useful lives. The value of the Company’s finite-lived intangible assets was based on the future expected net cash flows related to ZURAMPIC and DUZALLO (the “Lesinurad Products”), which included significant assumptions around future net sales and the respective investment to support these products. During the year ended December 31, 2018, the Company recorded an impairment charge of approximately $151.8 million to fully write-off its ZURAMPIC and DUZALLO intangible assets.
Impairment of Long-Lived Assets	Impairment of Long-Lived Assets The Company regularly reviews the carrying amount of its long-lived assets to determine whether indicators of impairment may exist, which warrant adjustments to carrying values or estimated useful lives. If indications of impairment exist, projected future undiscounted cash flows associated with the asset are compared to the carrying amount to determine whether the asset’s value is recoverable. If the carrying value of the asset exceeds such projected undiscounted cash flows, the asset will be written down to its estimated fair value.
Income Taxes	Income Taxes The Company provides for income taxes under the asset and liability method. Deferred tax assets and liabilities are determined based on differences between financial reporting and tax bases of assets and liabilities and are measured using the enacted tax rates in effect when the differences are expected to reverse. Deferred tax assets are reduced by a valuation allowance to reflect the uncertainty associated with their ultimate realization. The Company accounts for uncertain tax positions recognized in the consolidated financial statements in accordance with the provisions of ASC Topic 740, Income Taxes
Financing Costs	Financing Costs Financing costs include costs directly attributable to the Company’s offerings of its equity securities and its debt financings. Costs attributable to equity offerings are charged as a reduction to stockholders’ equity against the proceeds of the offering once the offering is completed. Costs attributable to debt financings are deferred and amortized to interest expense over the term of the debt using the effective interest method. Costs incurred in connection with convertible debt securities are allocated between the liability and equity components. In accordance with ASC 835, Interest
Leases	Leases Effective January 1, 2019, the Company adopted ASC Topic 842, Leases optional transition method ​ As part of the ASC 842 adoption, the Company elected certain practical expedients, which include: ​ ● Accounting policy election to use the short-term lease exception by asset class; and ● Election of the practical expedient package during transition, which includes: o An entity need not reassess whether any expired or existing contracts are or contain leases. o An entity need not reassess the classification for any expired or existing leases. As a result, all leases that were classified as operating leases in accordance with ASC 840 are classified as operating leases under ASC 842, and all leases that were classified as capital leases in accordance with ASC 840 are classified as finance leases under ASC 842. o An entity need not reassess initial direct costs for any existing leases. ​ Subsequent to the Company’s adoption of ASC 842, the Company elected the post-transition practical expedient, by class of underlying asset, to account for lease components and non-lease components together as a single component for the asset class of operating lease right-of-use real estate assets. ​ The Company’s lease portfolio for the year ended December 31, 2020 included: a lease for its headquarters location, a data center colocation lease, vehicle leases for its salesforce representatives, and leases for computer and office equipment. The Company determines if an arrangement is a lease at the inception of the contract. The asset component of the Company’s operating leases is recorded as operating lease right-of-use assets, and the liability component is recorded as current portion of operating lease liabilities and operating lease liabilities, net of current portion in the Company’s consolidated balance sheets. As of December 31, 2020, the Company did not record any finance leases. ​ Right-of-use assets and operating lease liabilities are recognized based on the present value of lease payments over the lease term at the lease inception date. Existing leases in the Company’s lease portfolio as of the adoption date were valued as of January 1, 2019. The Company uses an incremental borrowing rate based on the information available at lease inception in determining the present value of lease payments, if an implicit rate of return is not provided with the lease contract. Operating lease right-of-use assets are adjusted for incentives expected to be received. ​ Right-of-use assets and operating lease liabilities are remeasured upon certain modifications to leases using the present value of remaining lease payments and estimated incremental borrowing rate upon lease modification. ​ Lease cost is recognized on a straight-line basis over the lease term, and includes amounts related to short-term leases. The Company recognizes variable lease payments as operating expenses in the period in which the obligation for those payments is incurred. Variable lease payments primarily include common area maintenance, utilities, real estate taxes, insurance, and other operating costs that are passed on from the lessor in proportion to the space leased by the Company.
Derivative Assets and Liabilities	Derivative Assets and Liabilities In June 2015, the Company issued 2.25% Convertible Senior Notes due June 15, 2022 (the “2022 Convertible Notes”) and in August 2019, the Company issued 0.75% Convertible Senior Notes due 2024 (the “2024 Convertible Notes”) and 1.50% Convertible Senior Notes due 2026 (the “2026 Convertible Notes”) (together with the “2022 Convertible Notes” and the “2024 Convertible Notes”, the “Convertible Senior Notes”). In June 2015, in connection with the issuance of the 2022 Convertible Notes, the Company entered into convertible note hedge transactions (the “Convertible Note Hedges”). Concurrently with entering into the Convertible Note Hedges, the Company also entered into certain warrant transactions in which it sold note hedge warrants (the “Note Hedge Warrants”) to the Convertible Note Hedge counterparties to acquire shares of the Company’s Class A Common Stock, subject to customary anti-dilution adjustments (Note 11). In connection with the partial repurchase of the 2022 Convertible Notes in August 2019, the Company terminated its Convertible Note Hedges and Note Hedge Warrants proportionately. These instruments are derivative financial instruments under ASC Topic 815, Derivatives and Hedging These derivatives are recorded as assets or liabilities at fair value each reporting date and the fair value is determined using the Black-Scholes option-pricing model. The changes in fair value are recorded as a component of other (expense) income in the consolidated statements of operations. Significant inputs used to determine the fair value include the price per share of the Company’s Class A Common Stock on the date of valuation, expected term of the derivative instruments, strike prices of the derivative instruments, risk-free interest rate, and expected volatility of the Company’s Class A Common Stock. Changes to these inputs could materially affect the valuation of the Convertible Note Hedges and Note Hedge Warrants in future periods. In August 2019, in connection with the issuance of the 2024 Convertible Notes and the 2026 Convertible Notes, the Company entered into the Capped Calls. The Capped Calls cover the same number of shares of Class A Common Stock that initially underlie the 2024 Convertible Notes and the 2026 Convertible Notes (subject to anti-dilution and certain other adjustments). These instruments meet the conditions outlined in ASC 815 to be classified in stockholders’ equity (deficit) and are not subsequently remeasured as long as the conditions for equity classification continue to be met.
Revenue Recognition	Revenue Recognition The Company’s revenues are generated primarily through collaborative arrangements and license agreements related to the research and development and commercialization of linaclotide, as well as co-promotion arrangements in the U.S. The terms of the collaborative research and development, license, co-promotion and other agreements contain multiple performance obligations which may include (i) licenses, (ii) research and development activities, including participation on joint steering committees, (iii) the manufacture of finished drug product, API, or development materials for a partner, which are reimbursed at a contractually determined rate, and (iv) education or co-promotion activities by the Company’s clinical sales specialists. Non-refundable payments to the Company under these agreements may include (i) up-front license fees, (ii) payments for research and development activities, (iii) payments for the manufacture of finished drug product, API, or development materials, (iv) payments based upon the achievement of certain milestones, (v) payments for sales detailing, promotional support services and medical education initiatives, and (vi) royalties on product sales. The Company receives its share of the net profits or bears its share of the net losses from the sale of linaclotide in the U.S. through its collaboration agreement with AbbVie for North America. The Company has adopted a policy to recognize revenue net of tax withholdings, as applicable. Collaboration, License, Co-Promotion and Other Commercial Agreements Upon licensing intellectual property to a customer, the Company determines if the license is distinct from the other performance obligations identified in the arrangement. The Company recognizes revenues from the transaction price, including non-refundable, up-front fees allocated to the license when the license is transferred to the customer if the license has distinct benefit to the customer. For licenses that are combined with other promises, the Company assesses the nature of the combined performance obligation to determine whether the combined performance obligation is satisfied over time or at a point in time. For performance obligations that are satisfied over time, the Company evaluates the measure of progress each reporting period and, if necessary, adjusts the measure of performance and related revenue recognition. The Company’s license and collaboration agreements include milestone payments, such as development and other milestones. The Company evaluates whether the milestones are considered probable of being reached and estimates the amount to be included in the transaction price using the most likely amount method at the inception of the agreement. If it is probable that a significant revenue reversal would not occur, the associated milestone value is included in the transaction price. Milestone payments that are not within the control of the Company, such as regulatory approvals, are not considered probable of being achieved until those approvals are received. The transaction price is then allocated to each performance obligation on a relative standalone selling price basis, for which the Company recognizes revenue as or when the performance obligations under the contract are satisfied. The Company re-evaluates the probability of achievement of such milestones and any related constraint at each reporting period, and any adjustments are recorded on a cumulative catch-up basis. Agreements that include the supply of API or drug product for either clinical development or commercial supply at the customer’s discretion are generally considered as options. The Company assesses if these options provide a material right to its partner, and if so, they are accounted for as separate performance obligations. If the Company is entitled to additional payments when the customer exercises these options, any additional payments are recorded as revenue when the customer obtains control of the goods, which is typically upon shipment for sales of API and finished drug product. For agreements that include sales-based royalties, including milestone payments based on the level of sales, and the license is deemed to be the predominant item to which the royalties relate, the Company recognizes revenue when the related sales occur. Net Profit or Net Loss Sharing In accordance with ASC 808 Topic, Collaborative Arrangements Revenue from Contracts with Customers The Company’s collaborative arrangements revenues generated from sales of LINZESS in the U.S. are considered akin to sales-based royalties. In accordance with the sales-based royalty exception, the Company recognizes its share of the pre-tax commercial net profit or net loss generated from the sales of LINZESS in the U.S. in the period the product sales are earned, as reported by AbbVie, and related cost of goods sold and selling, general and administrative expenses as incurred by the Company and AbbVie. These amounts are partially determined based on amounts provided by AbbVie and involve the use of estimates and judgments, such as product sales allowances and accruals related to prompt payment discounts, chargebacks, governmental and contractual rebates, wholesaler fees, product returns, and co-payment assistance costs, which could be adjusted based on actual results in the future. The Company is highly dependent on AbbVie for timely and accurate information regarding net revenues from sales of LINZESS in the U.S. in accordance with both ASC 808 and ASC 606, and the related costs, in order to accurately report its results of operations. If the Company does not receive timely and accurate information or incorrectly estimates activity levels associated with the collaboration at a given point in time, the Company could be required to record adjustments in future periods. In accordance with ASC 606-10-55, Principal Agent Considerations Product Revenue, Net Product revenue consisted of sales of the Lesinurad Products, in the U.S. until the termination of the exclusive license to develop, manufacture, and commercialize in the U.S. products containing lesinurad as an active ingredient (the “Lesinurad License”) in January 2019. The Company sold the Lesinurad Products principally to a limited number of national wholesalers and selected regional wholesalers (the “Distributors”). The Distributors resold the Lesinurad Products to retail pharmacies and healthcare providers, who then sold to patients. Net product revenue was recognized when the Distributor obtained control of the Company’s product, which occurred at a point in time, typically upon shipment of Lesinurad Products to the Distributor. When the Company performed shipping and handling activities after the transfer of control to the Distributor (e.g., when control transfers prior to delivery), they were considered fulfillment activities, and accordingly, the costs were accrued for when the related revenue was recognized. The Company expensed incremental costs of obtaining a contract as and when incurred if the expected amortization period of the asset that the Company would have recognized was one year or less. The Company evaluated the creditworthiness of each of its Distributors to determine whether it was probable that a significant reversal in the amount of the cumulative revenue recognized would not occur. The Company calculated its net product revenue based on the wholesale acquisition cost that the Company charged its Distributors for the Lesinurad Products less variable consideration. The product revenue variable consideration consisted of estimates relating to (i) trade discounts and allowances, such as invoice discounts for prompt payment and distributor fees, (ii) estimated government and private payor rebates, chargebacks and discounts, such as Medicaid reimbursements, (iii) reserves for expected product returns and (iv) estimated costs of incentives offered to certain indirect customers including patients. These estimates would be adjusted based on actual results in the period such variances became known. Product revenue was recorded net of the trade discounts, allowances, rebates, chargebacks, discounts, product returns, and other incentives. Certain of these adjustments were recorded as an accounts receivable reserve, while certain of these adjustments were recorded as accrued expenses. ​ Sale of Active Pharmaceutical Ingredient During the years ended December 31, 2020, 2019, and 2018, the Company produced linaclotide API, finished drug product, finished goods, and/or development materials for certain of its partners. As of December 31, 2020, the Company is no longer responsible for the supply of linaclotide API, finished drug product, finished goods or development materials to its partners. As it relates to development materials and API produced for Astellas, the Company was reimbursed at a contracted rate. Such reimbursements were considered as part of revenue generated pursuant to the Astellas license agreement and are presented as collaborative arrangements revenue. Any linaclotide API, finished drug product, finished goods, and development materials AbbVie is responsible for producing for the U.S. are recognized in accordance with the cost-sharing provisions of the collaboration agreement with AbbVie for North America. Prior to the execution of the Amended AstraZeneca Agreement in September 2019, any linaclotide API, finished drug product, and development materials produced for AstraZeneca for China (including Hong Kong and Macau) were recognized in accordance with the cost-sharing provisions of the AstraZeneca collaboration agreement. The Company recognized revenue on linaclotide API, finished drug product, finished goods, and development materials when control has transferred to the partner, which generally occurs upon shipment after the material passed all quality testing required for acceptance by the partner. Other The Company’s deferred revenue balance consists of advance billings and payments received from customers in excess of revenue recognized.
Cost of Revenues	Cost of Revenues Cost of revenues includes cost related to the sales of linaclotide API and finished drug product, as well as the cost of product revenue related to sales of the Lesinurad Products in the U.S. Cost related to the sales of linaclotide API, finished drug product, and finished goods are generally recognized upon shipment to certain of the Company’s partners outside of the U.S. The Company’s cost of revenues for linaclotide consists of the internal and external costs of producing such API and finished drug product. Cost of product revenue related to the sales of the Lesinurad Products in the U.S. includes the cost of producing finished goods that correspond with product revenue for the reporting period, such as third-party supply and overhead costs, as well as certain period costs related to freight, packaging, stability and quality testing, and customer acquisition.
Research and Development Costs	Research and Development Costs The Company generally expenses research and development costs to operations as incurred. The Company capitalizes nonrefundable advance payments made by the Company for research and development activities and defers expense recognition until the related goods are received or the related services are performed. Research and development expenses are comprised of costs incurred in performing research and development activities, including salary, benefits, share-based compensation, and other employee-related expenses; laboratory supplies and other direct expenses; facilities expenses; overhead expenses; third-party contractual costs relating to nonclinical studies and clinical trial activities and related contract manufacturing expenses, development of manufacturing processes and regulatory registration of third-party manufacturing facilities; licensing fees for the Company’s product candidates; and other outside expenses. The Company has certain collaboration agreements pursuant to which it shares or has shared research and development expenses related to linaclotide. The Company records expenses incurred under such linaclotide collaboration arrangements as research and development expense. Prior to the execution of the Amended AstraZeneca Agreement in September 2019, under the Company’s collaboration agreement with AstraZeneca for China (including Hong Kong and Macau), the Company was reimbursed for certain research and development expenses and it netted these reimbursements against its research and development expenses as incurred. In connection with the execution of the Amended AstraZeneca Agreement, AstraZeneca is fully responsible for all research and development costs incurred related to the development, manufacture, and commercialization of linaclotide in China (including Hong Kong and Macau). Under the Company’s collaboration agreement with AbbVie for North America, the Company is reimbursed for certain research and development expenses and nets these reimbursements against its research and development expenses as incurred. Amounts owed to AbbVie or AstraZeneca under the Company’s respective collaboration agreements were recorded as incremental research and development expense. ​
Restructuring Expenses	Restructuring Expenses Restructuring expenses are comprised primarily of costs associated with exit and disposal activities in accordance with ASC 420, Exit or Disposal Cost Obligations
Selling, General and Administrative Expenses	Selling, General and Administrative Expenses The Company expenses selling, general and administrative costs to operations as incurred. Selling, general and administrative expenses consist primarily of compensation, benefits and other employee-related expenses for personnel in the Company’s administrative, finance, legal, information technology, business development, commercial, sales, marketing, communications and human resource functions. Other costs include the legal costs of pursuing patent protection of the Company’s intellectual property, general and administrative related facility costs, insurance costs and professional fees for accounting, tax, consulting, legal and other services. Prior to the execution of the Amended AstraZeneca Agreement, the Company was reimbursed for certain selling, general and administrative expenses and the Company netted these reimbursements against the Company’s selling, general and administrative expenses as incurred. In connection with the Amended AstraZeneca Agreement, effective in September 2019, AstraZeneca will be fully responsible for all costs related to the development, manufacture, and commercialization of linaclotide in China (including Hong Kong and Macau). The Company includes AbbVie’s selling, general and administrative cost-sharing payments in the calculation of the net profits and net losses from the sale of LINZESS in the U.S. and presents the net payment to or from AbbVie as collaboration expense or collaborative arrangements revenue, respectively.
Share-Based Compensation Expense	Share-Based Compensation Expense The Company grants awards under its share-based compensation programs, including stock awards, restricted stock awards (“RSAs”), restricted stock units (“RSUs”) (including both time-based and performance-based RSUs), stock options, and shares issued under the Company’s employee stock purchase plan (“ESPP”). Share-based compensation is recognized as expense in the consolidated statements of operations based on the grant date fair value over the requisite service period, net of estimated forfeitures. The Company estimates forfeitures over the requisite service period using historical forfeiture activity and records share-based compensation expense only for those awards that are expected to vest. The Company estimates the fair value of stock options using the Black-Scholes option-pricing model, which requires the use of subjective assumptions including volatility and expected term, among others. The fair value of stock awards, RSAs, and RSUs is based on the market value of the Company’s Class A Common Stock on the date of grant, with the exception of performance-based RSUs with market conditions, which are measured using the Monte Carlo simulation method on the date of grant (Note 14). Discounted stock purchases under the Company’s ESPP are valued on the first date of the offering period using the Black-Scholes option-pricing model to compute the fair value of the lookback provision plus the purchase discount. For awards that vest based on service conditions and market conditions, the Company uses a straight-line method to recognize compensation expense over the respective service period. For awards that contain performance conditions, the Company determines the appropriate amount to expense at each reporting date based on the anticipated achievement of performance targets, which requires judgement, including forecasting the achievement of future specified targets. At the date performance conditions are determined to be probable of achievement, the Company records a cumulative expense catch-up, with remaining expense amortized over the remaining service period. Throughout the performance period, the Company re-assesses the estimated performance and updates the number of performance-based awards that it believes will ultimately vest. Discounted stock purchases under the Company’s ESPP are recognized over the offering period. Compensation expense related to modified awards is measured based on the fair value for the awards as of the modification date. Any incremental compensation expense arising from the excess of the fair value of the awards on the modification date compared to the fair value of the awards immediately before the modification date is recognized at the modification date or ratably over the requisite remaining service period, as appropriate. While the assumptions used to calculate and account for share-based compensation awards represent management’s best estimates, these estimates involve inherent uncertainties and the application of management’s judgment. As a result, if revisions are made to the Company’s underlying assumptions and estimates, the Company’s share-based compensation expense could vary significantly from period to period.
Patent Costs	Patent Costs The Company incurred and recorded as operating expense legal and other fees related to patents of approximately $2.3 million, approximately $7.8 million, and approximately $5.0 million for the years ended December 31, 2020, 2019 and 2018, respectively. These costs were charged to selling, general and administrative expenses as incurred.
Net Income (Loss) Per Share	Net Income (Loss) Per Share Basic net income (loss) per common share is computed by dividing the net income (loss) by the weighted average number of common shares outstanding during the period. Diluted net income (loss) per common share is computed by dividing net income (loss) by the diluted number of shares outstanding during the period. Except where the result would be antidilutive to net income (loss), diluted net income (loss) per common share is computed assuming the conversion of the 2022 Convertible Notes, the 2024 Convertible Notes and the 2026 Convertible Notes, the exercise of outstanding common stock options and the vesting of RSUs and RSAs (using the treasury stock method), as well as their related income tax effects.
Comprehensive Income (Loss)	Comprehensive Income (Loss) Comprehensive income (loss) is defined as the change in equity of a business enterprise during a period from transactions, and other events and circumstances from non-owner sources and consists of net income (loss) and changes in unrealized gains and losses on available-for-sale debt securities in the periods presented in the Company’s consolidated statements of comprehensive income (loss).
Subsequent Events	Subsequent Events The Company considers events or transactions that have occurred after the balance sheet date of December 31, 2020, but prior to the filing of the financial statements with the Securities and Exchange Commission (“SEC”) to provide additional evidence relative to certain estimates or to identify matters that require additional recognition or disclosure. Subsequent events have been evaluated through the filing of the financial statements accompanying this Annual Report on Form 10-K.
New Accounting Pronouncements	New Accounting Pronouncements From time to time, new accounting pronouncements are issued by the Financial Accounting Standards Board (the “FASB”) or other standard setting bodies that are adopted by the Company as of the specified effective date. Except as set forth below, the Company did not adopt any new accounting pronouncements during the year ended December 31, 2020 that had a material effect on its consolidated financial statements. In June 2016, the FASB issued Accounting Standards Update (“ASU”) No. 2016-13, Measurement of Credit Losses on Financial Instruments Codification Improvements to Topic 326, Financial Instruments—Credit Losses Topic 815, Derivatives and Hedging Topic 825, Financial Instruments Financial Instruments—Credit Losses (Topic 326) Targeted Transition Relief Financial Instruments—Credit Losses (Topic 326) Derivatives and Hedging (Topic 815) Leases (Topic 842): Effective Date Codification Improvements to Topic 326, Financial Instruments—Credit Losses Financial Instruments—Credit Losses (Topic 326) and Leases (Topic 842) Amendments to SEC Paragraphs Pursuant to SEC Staff Accounting Bulletin No. 119 and Update to SEC Section on Effective Date Related to Accounting Standards Update No. 2016-02, Leases (Topic 842) March 31, 2020 In January 2017, the FASB issued ASU No. 2017-04, Intangibles—Goodwill and Other (Topic 350) March 31, 2020 In August 2018, the FASB issued ASU No. 2018-13, Fair Value Measurement (Topic 820): Disclosure Framework— Changes to the Disclosure Requirement for Fair Value Measurement March 31, 2020 In August 2018, the FASB issued ASU No. 2018-15, Intangibles—Goodwill and Other—Internal Use Software (Subtopic 350-40): Customer’s Accounting for Implementation Costs Incurred in a Cloud Computing Arrangement that is a Service Contract (a consensus of the FASB Emerging Issues Task Force) prospective transition method March 31, 2020 In October 2018, the FASB issued ASU No. 2018-17, Consolidation (Topic 810): Targeted Improvements to Related Party Guidance for Variable Interest Entities March 31, 2020 In December 2019, the FASB issued ASU No. 2019-12, Income Taxes (Topic 740): Simplifying the Accounting for Income Taxes In August 2020, the FASB issued ASU No. 2020-06, Debt—Debt with Conversion and Other Options (Subtopic 470-20) and Derivatives and Hedging— Contracts in Entity’s Own Equity (Subtopic 815-40): Accounting for Convertible Instruments and Contracts in an Entity’s Own Equity Other recent accounting pronouncements issued, but not yet effective, are not expected to be applicable to the Company or have a material effect on the consolidated financial statements upon future adoption.

Summary of Significant Accoun_3

Summary of Significant Accounting Policies (Tables)	12 Months Ended
	Dec. 31, 2020
Table Text Blocks
Schedule of percentages of revenue and accounts receivable recognized from significant customers	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Accounts ​ Revenue ​ ​ December 31, ​ Year Ended December 31, ​ 2020 2019 2020 2019 2018 Collaborative Partner: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ AbbVie (North America and Europe) 76 % 90 % 96 % 78 % 77 % Astellas (Japan) 1 % 8 % 1 % 13 % 20 %
Schedule of estimated useful life	​ ​ ​ ​ ​ ​ Estimated Useful Life Asset Description (In Years) Laboratory equipment 5 ​ Computer and office equipment 3 ​ Furniture and fixtures 7 ​ Software 3 ​ ​

Cyclerion Separation (Tables)

Cyclerion Separation (Tables)	12 Months Ended
	Dec. 31, 2020
Table Text Blocks
Summary of assets and liabilities transferred in separation	​ ​ ​ ​ ​ ​ ​ ​ ​ As of April 1, 2019 ​ Assets: ​ ​ ​ ​ Prepaid expenses and other current assets ​ $ 1,169 ​ Property and equipment, net ​ ​ 10,241 ​ Other assets ​ ​ 21 ​ ​ ​ $ 11,431 ​ Liabilities: ​ ​ ​ ​ Accrued research and development costs ​ $ 5,673 ​ Accrued expenses and other current liabilities ​ ​ 3,149 ​ ​ ​ $ 8,822 ​ Net Assets Transferred to Cyclerion ​ $ 2,609 ​
Summary of the discontinued operations	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Year Ended December 31, ​ ​ 2019 2018 Costs and expenses: ​ ​ ​ ​ ​ ​ ​ Research and development ​ $ 21,792 ​ $ 65,443 ​ Selling, general and administrative ​ ​ 15,646 ​ 21,615 ​ Restructuring expenses ​ ​ — ​ ​ 1,164 ​ Net loss from discontinued operations ​ $ 37,438 ​ $ 88,222 ​

Net Income (Loss) Per Share (Ta

Net Income (Loss) Per Share (Tables)	12 Months Ended
	Dec. 31, 2020
Table Text Blocks
Schedule of computation of basic and diluted net loss per common share	The following table sets forth the computation of basic and diluted net income (loss) per common share (in thousands, except per share amounts): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Year Ended December 31, ​ 2020 ​ 2019 2018 Numerator: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Net income (loss) ​ $ 106,176 ​ $ 21,505 ​ $ (282,368) ​ Denominator: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Weighted average number of common shares outstanding used in net income (loss) per share — basic ​ 159,427 ​ 156,023 ​ 152,634 ​ Effect of dilutive securities: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Stock options ​ ​ 367 ​ ​ — ​ ​ — ​ Time-based restricted stock units ​ ​ 766 ​ ​ — ​ ​ — ​ Performance-based restricted stock units ​ ​ 1 ​ ​ — ​ ​ — ​ Restricted stock ​ ​ 94 ​ ​ — ​ ​ — ​ Dilutive potential common shares ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Weighted average number of common shares outstanding used in net income (loss) per share — diluted ​ ​ 160,655 ​ 156,023 ​ ​ 152,634 ​ Net income (loss) per share — basic ​ ​ 0.67 ​ 0.14 ​ ​ (1.85) ​ Net income (loss) per share — diluted ​ $ 0.66 ​ $ 0.14 ​ $ (1.85) ​
Schedule of potentially dilutive securities that have been excluded from computation of diluted weighted average shares outstanding	The outstanding securities have been excluded from the computation of diluted weighted average shares outstanding, as applicable, as their effect would be anti-dilutive (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Year Ended December 31, ​ 2020 2019 2018 Stock options 11,746 17,194 20,457 ​ Restricted stock awards 2 182 65 ​ Time-based restricted stock units ​ 209 ​ 3,207 ​ 3,058 ​ Performance-based restricted stock units ​ 93 ​ — ​ — ​ Note Hedge Warrants ​ 8,318 ​ 8,318 ​ 20,250 ​ 2022 Convertible Notes ​ 8,318 ​ 8,318 ​ 20,250 ​ 2024 Convertible Notes ​ 14,934 ​ 14,934 ​ — ​ 2026 Convertible Notes ​ 14,934 ​ 14,934 ​ — ​ ​ 58,554 67,087 64,080 ​

Collaboration, License, Promo_2

Collaboration, License, Promotion and Other Commercial Agreements (Tables)	12 Months Ended
	Dec. 31, 2020
Table Text Blocks
Schedule of revenue attributable to transactions from collaboration and license arrangements	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Year Ended December 31, Collaborative Arrangements Revenue 2020 2019 2018 Linaclotide Collaboration and License Agreements: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ AbbVie (North America) ​ $ 370,902 $ 327,591 $ 266,177 ​ AbbVie (Europe and other) ​ ​ 2,196 ​ ​ 1,718 ​ ​ 1,146 ​ AstraZeneca (China, including Hong Kong and Macau) ​ ​ 682 ​ 32,628 ​ — ​ Astellas (Japan) ​ ​ 2,128 ​ 10,147 ​ — ​ Co-Promotion and Other Agreements: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ AbbVie (VIBERZI) (1) ​ ​ — ​ ​ 3,723 ​ ​ 4,290 ​ Alnylam (GIVLAARI) ​ ​ 4,302 ​ ​ 2,000 ​ ​ — ​ Other ​ ​ 1,335 ​ ​ 1,845 ​ ​ 1,226 ​ Total collaborative arrangements revenue ​ $ 381,545 ​ $ 379,652 ​ $ 272,839 ​ Sale of API ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Linaclotide Agreements: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Astellas (Japan) ​ $ 2,017 ​ $ 45,788 ​ $ 69,599 ​ AstraZeneca (China, including Hong Kong and Macau) ​ ​ 5,540 ​ ​ 2,973 ​ ​ — ​ Other ​ ​ 421 ​ ​ — ​ ​ 756 ​ Total sale of API ​ $ 7,978 ​ $ 48,761 ​ $ 70,355 ​ (1) The Company had an agreement with AbbVie to perform sales detailing activities for VIBERZI® (eluxadoline) which terminated as of December 31, 2019.
AbbVie
Table Text Blocks
Schedule of revenue attributable to transactions from collaboration and license arrangements	The Company recognized collaborative arrangements revenue from the AbbVie collaboration agreement for North America during the years ended December 31, 2020, 2019, and 2018 as follows (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Year Ended December 31, ​ 2020 2019 2018 Collaborative arrangements revenue related to sales of LINZESS in the U.S. ​ $ 368,603 ​ $ 325,429 ​ $ 264,243 ​ Royalty revenue ​ 2,299 ​ 2,162 ​ 1,934 ​ Total collaborative arrangements revenue ​ $ 370,902 ​ $ 327,591 ​ $ 266,177 ​
Schedule of amount recorded by the Company for share of net loss related to collaborative arrangement	The following table presents the amounts recorded by the Company for commercial efforts related to LINZESS in the U.S. in the years ended December 31, 2020, 2019, and 2018 (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Year Ended December 31, ​ 2020 2019 2018 Ironwood's collaborative arrangement revenue ​ $ 368,603 ​ $ 325,429 ​ $ 264,243 ​ Selling, general and administrative costs incurred by the Company (1) ​ (39,312) ​ (38,123) ​ (42,435) ​ Ironwood's share of net profits (2) ​ $ 329,291 ​ $ 287,306 ​ $ 221,808 ​ ​ (1) Includes Ironwood’s selling, general and administrative expenses attributable to the cost-sharing arrangement with AbbVie. Excludes approximately $0.6 million, approximately $2.4 million, and approximately $2.2 million for the years ended December 31, 2020, 2019, and 2018 respectively, related to patent prosecution and patent litigation costs recognized in connection with the collaboration agreement with AbbVie. (2) Ironwood has recalculated its share of net profit on sales of LINZESS in the U.S. to conform with AbbVie’s recast of historically reported LINZESS U.S. net sales (previously reported by Allergan).

Fair Value of Financial Instr_2

Fair Value of Financial Instruments (Tables)	12 Months Ended
	Dec. 31, 2020
Table Text Blocks
Schedule of assets and liabilities measured at fair value on a recurring basis	The following tables present the assets and liabilities the Company has measured at fair value on a recurring basis (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Fair Value Measurements at Reporting Date Using ​ ​ ​ Quoted Prices in Significant Other Significant ​ ​ ​ ​ ​ Active Markets for ​ Observable ​ Unobservable ​ ​ December 31, ​ Identical Assets ​ Inputs ​ Inputs ​ ​ 2020 ​ (Level 1) ​ (Level 2) ​ (Level 3) ​ Assets: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Cash and cash equivalents: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Money market funds ​ $ 349,014 ​ $ 349,014 ​ $ — ​ $ — ​ Restricted cash: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Money market funds ​ ​ 2,221 ​ ​ 2,221 ​ ​ — ​ ​ — ​ Convertible note hedges ​ ​ 13,065 ​ ​ — ​ ​ — ​ ​ 13,065 ​ Total assets measured at fair value ​ $ 364,300 ​ $ 351,235 ​ $ — ​ $ 13,065 ​ Liabilities: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Note hedge warrants ​ $ 12,088 ​ $ — ​ $ — ​ $ 12,088 ​ Total liabilities measured at fair value ​ $ 12,088 ​ $ — ​ $ — ​ $ 12,088 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Fair Value Measurements at Reporting Date Using ​ ​ ​ Quoted Prices in Significant Other Significant ​ ​ ​ ​ ​ Active Markets for ​ Observable ​ Unobservable ​ ​ December 31, ​ Identical Assets ​ Inputs ​ Inputs ​ ​ 2019 ​ (Level 1) ​ (Level 2) ​ (Level 3) ​ Assets: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Cash and cash equivalents: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Money market funds ​ $ 139,190 ​ $ 139,190 ​ $ — ​ $ — ​ Repurchase agreements ​ ​ 37,800 ​ ​ 37,800 ​ ​ — ​ ​ — ​ Restricted cash: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Money market funds ​ 2,221 ​ 2,221 ​ — ​ — ​ Convertible note hedges ​ ​ 31,366 ​ ​ — ​ ​ — ​ ​ 31,366 ​ Total assets measured at fair value ​ $ 210,577 ​ $ 179,211 ​ $ — ​ $ 31,366 ​ Liabilities: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Note hedge warrants ​ $ 24,260 ​ $ — ​ $ — ​ $ 24,260 ​ Total liabilities measured at fair value ​ $ 24,260 ​ $ — ​ $ — ​ $ 24,260 ​
Schedule of assumptions used in fair market valuations	The following inputs were used in the fair market valuation of the Convertible Note Hedges and Note Hedge Warrants as of December 31, 2020 and 2019: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, ​ December 31, ​ ​ 2020 ​ 2019 ​ ​ ​ Convertible Note Hedge ​ Convertible Note Hedge ​ ​ Note Hedges ​ Warrants Note Hedges ​ Warrants Risk-free interest rate (1) ​ ​ 0.1 % ​ 0.1 % ​ 1.6 % ​ 1.6 % Expected term ​ 1.5 ​ 2.0 ​ ​ 2.5 ​ 3.0 ​ Stock price (2) ​ $ 11.39 ​ $ 11.39 ​ $ 13.31 ​ $ 13.31 ​ Strike price (3) ​ $ 14.51 ​ $ 18.82 ​ $ 14.51 ​ $ 18.82 ​ Common stock volatility (4) ​ ​ 46.7 % ​ 50.3 % ​ 49.1 % ​ 46.5 % Dividend yield (5) ​ — % — % — % — % (1) Based on U.S. Treasury yield curve, with terms commensurate with the expected terms of the Convertible Note Hedges and the Note Hedge Warrants. (2) The closing price of the Company’s Class A Common Stock on the last trading days of the years ended December 31, 2020 and 2019, respectively. (3) As per the respective agreements for the Convertible Note Hedges and Note Hedge Warrants. (4) Expected volatility based on historical volatility of the Company’s Class A Common Stock. (5) The Company has not paid and does not anticipate paying cash dividends on its shares of common stock in the foreseeable future; therefore, the expected dividend yield is assumed to be zero . ​
Schedule of the change in Level 3 convertible note derivatives	The following table reflects the change in the Company's Level 3 Convertible Note Hedges and Note Hedge Warrants from December 31, 2018 through December 31, 2020 (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Convertible ​ Note Hedge ​ ​ Note Hedges Warrants Balance at December 31, 2018 ​ $ 41,020 ​ $ (33,763) ​ Cash settlement (received) paid upon early termination of derivatives (Note 11) ​ ​ (28,909) ​ ​ 25,735 ​ Change in fair value, recorded as a component of gain (loss) on derivatives ​ ​ 19,255 ​ ​ (16,232) ​ Balance at December 31, 2019 ​ $ 31,366 ​ $ (24,260) ​ Change in fair value, recorded as a component of (loss) gain on derivatives ​ ​ (18,301) ​ ​ 12,172 ​ Balance at December 31, 2020 ​ $ 13,065 ​ $ (12,088) ​

Leases (Tables)

Leases (Tables)	12 Months Ended
	Dec. 31, 2020
Table Text Blocks
Schedule of components of lease cost and supplemental cash flow information	Lease cost is recognized on a straight-line basis over the lease term. The components of lease cost for the year ended December 31, 2020 and 2019 are as follows (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Year Ended December 31, ​ ​ ​ 2020 ​ 2019 ​ Operating lease cost during period, net (1) ​ $ 2,530 ​ $ 16,452 ​ Variable lease payments ​ ​ — ​ ​ 1,526 ​ Short-term lease cost ​ ​ 1,420 ​ ​ 1,512 ​ Total lease cost ​ $ 3,950 ​ $ 19,490 ​ (1) Operating lease cost is presented net of approximately $0.3 million of sublease income for the year ended December 31, 2019 related to a sublease agreement between Ironwood and Cyclerion executed upon Separation. The sublease agreement terminated in May 2019. ​ Supplemental cash flow information related to leases for the periods reported is as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Year Ended December 31, ​ ​ ​ 2020 ​ 2019 ​ Right-of-use assets obtained in exchange for new operating lease upon adoption of ASC 842 (in thousands) ​ $ — ​ ​ $ 88,299 ​ ​ Adjustment to right-of-use assets as a result of the lease modification upon Separation (in thousands) ​ ​ — ​ ​ ​ (40,427) ​ ​ Adjustment to right-of-use assets as a result of the termination of the Binney Street Lease (in thousands) ​ ​ — ​ ​ ​ (34,440) ​ ​ Right-of-use assets obtained in exchange for new operating lease liabilities upon execution of Summer Street Lease (in thousands) ​ ​ — ​ ​ ​ 18,452 ​ ​ Cash paid for amounts included in the measurement of lease liabilities (in thousands) ​ ​ 1,146 ​ ​ ​ 18,598 ​ ​ Weighted-average remaining lease term of operating leases (in years) ​ ​ 9.3 ​ ​ ​ 10.2 ​ ​ Weighted-average discount rate of operating leases ​ ​ 5.8 % ​ ​ 5.8 % ​ ​
Schedule of future minimum lease payments under non-cancelable operating leases	Future minimum lease payments under non-cancelable operating leases as of December 31, 2020 are as follows (in thousands): ​ ​ ​ ​ ​ ​ Operating ​ Lease ​ ​ Payments 2021 ​ $ 3,128 2022 ​ ​ 3,129 2023 ​ ​ 3,065 2024 ​ ​ 3,126 2025 ​ 3,189 2026 and thereafter ​ 14,856 Total future minimum lease payments ​ ​ 30,493 Less: present value adjustment ​ ​ (7,047) Operating lease liabilities at December 31, 2020 ​ ​ 23,446 Less: current portion of operating lease liabilities ​ ​ (3,128) Operating lease liabilities, net of current portion ​ $ 20,318

Property and Equipment (Tables)

Property and Equipment (Tables)	12 Months Ended
	Dec. 31, 2020
Table Text Blocks
Schedule of property and equipment	Property and equipment, net consisted of the following (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, ​ 2020 2019 Software ​ $ 8,615 ​ $ 9,568 ​ Leasehold improvements ​ 7,407 ​ 7,318 ​ Laboratory equipment ​ 1,898 ​ 2,193 ​ Furniture and fixtures ​ 1,517 ​ 1,508 ​ Computer and office equipment ​ 1,297 ​ 1,293 ​ Construction in process ​ — ​ 631 ​ ​ ​ 20,734 ​ 22,511 ​ Less accumulated depreciation and amortization ​ (11,805) ​ (10,082) ​ ​ ​ $ 8,929 ​ $ 12,429 ​

Accrued Expenses and Other Cu_2

Accrued Expenses and Other Current Liabilities (Tables)	12 Months Ended
	Dec. 31, 2020
Table Text Blocks
Schedule of accrued expenses and other current liabilities	Accrued expenses and other current liabilities consisted of the following (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, ​ 2020 2019 Accrued incentive compensation ​ $ 8,719 ​ $ 11,760 ​ Accrued vacation ​ ​ 2,625 ​ ​ 2,540 ​ Professional fees ​ 530 ​ 1,421 ​ Salaries ​ ​ 627 ​ ​ 2,973 ​ Other employee benefits ​ ​ 1,442 ​ ​ 1,260 ​ Restructuring liabilities ​ ​ 10,510 ​ ​ 179 ​ Other ​ 2,033 ​ 10,332 ​ ​ ​ $ 26,486 ​ $ 30,465 ​

Notes Payable (Tables)

Notes Payable (Tables)	12 Months Ended
	Dec. 31, 2020
Table Text Blocks
Schedule of outstanding Convertible Note	The Company’s outstanding balances for the convertible senior notes as of December 31, 2020 and 2019 consisted of the following (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, ​ ​ ​ 2020 ​ 2019 ​ Liability component: ​ ​ ​ ​ ​ ​ Principal: ​ ​ ​ ​ ​ 2022 Convertible Notes ​ $ 120,699 ​ $ 120,699 ​ 2024 Convertible Notes ​ ​ 200,000 ​ ​ 200,000 ​ 2026 Convertible Notes ​ ​ 200,000 ​ ​ 200,000 ​ Less: unamortized debt discount ​ ​ (83,900) ​ ​ (104,700) ​ Less: unamortized debt issuance costs ​ ​ (6,543) ​ ​ (8,005) ​ Net carrying amount ​ $ 430,256 ​ $ 407,994 ​ Equity component: ​ ​ ​ ​ ​ ​ ​ 2022 Convertible Notes ​ ​ 19,807 ​ ​ 19,807 ​ 2024 Convertible Notes ​ ​ 41,152 ​ ​ 41,152 ​ 2026 Convertible Notes ​ ​ 51,350 ​ ​ 51,350 ​ Total equity component ​ $ 112,309 ​ $ 112,309 ​
Schedule of interest expense related to Convertible Notes	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Year Ended December 31, ​ 2020 2019 ​ 2018 Contractual interest expense ​ $ 7,216 ​ $ 7,361 ​ $ 7,553 Amortization of debt issuance costs ​ ​ 1,462 ​ ​ 1,190 ​ ​ 971 Amortization of debt discount ​ ​ 20,800 ​ ​ 17,683 ​ ​ 15,437 Total interest expense ​ $ 29,478 ​ $ 26,234 ​ $ 23,961
Schedule of future minimum payments details of debt	​ ​ ​ ​ ​ 2021 ​ $ 7,216 2022 ​ ​ 126,557 2023 ​ ​ 4,500 2024 ​ ​ 203,750 2025 ​ ​ 3,000 2026 ​ ​ 201,500 Total future minimum payments under the convertible senior notes ​ 546,523 Less: amounts representing interest ​ ​ (25,824) Less: unamortized debt discount ​ ​ (83,900) Less: unamortized debt issuance costs ​ ​ (6,543) Convertible senior notes balance ​ $ 430,256 ​

Employee Stock Benefit Plans (T

Employee Stock Benefit Plans (Tables)	12 Months Ended
	Dec. 31, 2020
Table Text Blocks
Summary of expense recognized for share-based compensation arrangements	The following table summarizes share-based compensation expense by award type (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Year Ended December 31, ​ 2020 2019 2018 Stock options ​ $ 7,680 ​ $ 12,526 ​ $ 20,478 ​ Time-based restricted stock units ​ ​ 18,624 ​ ​ 15,488 ​ ​ 17,160 ​ Performance-based restricted stock units ​ 2,190 ​ — ​ — ​ Restricted stock awards ​ 1,886 ​ 2,095 ​ 2,330 ​ Employee stock purchase plan ​ 722 ​ 1,115 ​ 1,097 ​ Stock awards ​ 73 ​ 54 ​ 17 ​ ​ ​ $ 31,175 ​ $ 31,278 ​ $ 41,082 ​
Share-based compensation expense reflected in the condensed consolidated statements of operations	The following table summarizes the share-based compensation expense reflected in the consolidated statements of operations (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Years Ended December 31, ​ 2020 2019 2018 Research and development ​ $ 5,569 ​ $ 6,343 ​ $ 11,500 ​ Selling, general and administrative ​ 23,825 ​ 24,281 ​ 27,440 ​ Restructuring expenses ​ ​ 1,781 ​ ​ 654 ​ ​ 2,142 ​ ​ ​ $ 31,175 ​ $ 31,278 ​ $ 41,082 ​
Schedule of weighted-average assumptions used to estimate the fair value of Relative TSR PSUs	​ ​ ​ ​ ​ ​ ​ Year Ended December 31, ​ 2020 ​ ​ ​ Fair value of common stock $ 11.78 ​ Expected volatility 53.3 % Expected term (in years) 2.8 ​ Risk-free interest rate 1.0 % Expected dividend yield — % ​
Summary of restricted stock activity	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Weighted- ​ ​ ​ Average ​ ​ Number of ​ Grant Date ​ ​ Shares ​ Fair Value Unvested as of December 31, 2019 181,648 ​ $ 10.76 ​ Granted 246,500 ​ ​ 10.16 ​ Vested (181,648) ​ ​ 10.46 ​ Forfeited — ​ ​ — ​ Unvested as of December 31, 2020 246,500 ​ $ 10.38 ​ ​
Schedule of weighted-average assumptions used to estimate the fair value of the stock options using the Black-Scholes option-pricing model	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Years Ended December 31, ​ ​ ​ 2020 ​ 2019 ​ 2018 ​ Expected volatility ​ 46.6 % 46.3 % 43.7 % Expected term (in years) ​ 6.1 ​ 6.1 ​ 6.0 ​ Risk-free interest rate ​ 1.5 % 2.5 % 2.7 % Expected dividend yield ​ — % — % — %
Summary of stock option activity	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Weighted- ​ Weighted- ​ ​ ​ ​ ​ Number of ​ Average ​ Average ​ Aggregate ​ ​ Stock ​ Exercise ​ Contractual ​ Intrinsic ​ ​ Options ​ Price (1) ​ Life ​ Value ​ ​ ​ ​ ​ ​ ​ (in years) ​ (in thousands) Outstanding at December 31, 2019 17,194,239 ​ $ 12.13 ​ 5.11 ​ $ 25,226 ​ Granted 55,000 ​ ​ 12.84 ​ — ​ ​ — ​ Exercised (1,735,081) ​ ​ 10.21 ​ — ​ ​ — ​ Cancelled (2,054,487) ​ ​ 13.00 ​ — ​ ​ — ​ Outstanding at December 31, 2020 13,459,671 ​ ​ 12.25 ​ 4.27 ​ ​ 5,613 ​ Vested or expected to vest at December 31, 2020 13,280,456 ​ ​ 12.26 ​ 4.23 ​ ​ 5,575 ​ Exercisable at December 31, 2020 11,963,812 ​ ​ 12.26 ​ 3.90 ​ ​ 5,371 ​ ​ (1) Exercise prices relating to stock options granted prior to the Separation have not been adjusted to reflect the effect of the Separation on the stock options. ​
Schedule of unrecognized share-based compensation expense, net of estimated forfeitures by type of awards and weighted-average period	​ ​ ​ ​ ​ ​ ​ ​ ​ Unrecognized Weighted-Average ​ ​ Expense, Net ​ Remaining ​ ​ of Estimated ​ Recognition ​ ​ ​ Forfeitures ​ Period ​ ​ (in thousands) ​ (in years) Type of award: ​ ​ ​ ​ ​ ​ Stock options with time-based vesting ​ $ 6,557 ​ 1.84 ​ Restricted stock awards ​ ​ 1,473 ​ 0.92 ​ Time-based restricted stock units ​ ​ 26,934 ​ 2.22 ​ Performance-based restricted stock units ​ ​ 3,291 ​ 1.70 ​ Stock options with time-based and performance-based vesting (1) ​ ​ 88 ​ — ​ (1) The weighted-average remaining recognition period cannot be determined for performance-based or time-accelerated options due to the nature of such awards, as detailed above. ​
Time-based Restricted Stock Units
Table Text Blocks
Summary of RSU activity	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Weighted- ​ ​ ​ ​ ​ Average ​ ​ ​ Number ​ Grant Date ​ ​ of RSUs Fair Value Outstanding as of December 31, 2019 3,207,089 ​ $ 12.33 ​ Granted ​ 2,708,200 ​ ​ 11.59 ​ Vested and released ​ (965,625) ​ ​ 12.37 ​ Forfeited ​ (779,038) ​ ​ 11.96 ​ Outstanding as of December 31, 2020 4,170,626 ​ $ 11.90 ​ ​
Performance-based Restricted Stock Units
Table Text Blocks
Summary of RSU activity	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Weighted- ​ ​ ​ ​ ​ Average ​ ​ ​ Number ​ Grant Date ​ ​ of RSUs Fair Value (1) Outstanding as of December 31, 2019 — ​ $ — ​ Granted ​ 586,157 ​ ​ 12.48 ​ Vested and released ​ — ​ ​ — ​ Forfeited ​ — ​ ​ — ​ Outstanding as of December 31, 2020 586,157 ​ $ 12.48 ​ ​

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2020
Table Text Blocks
Reconciliation of income taxes from continuing operations computed using U.S. federal statutory rate to that reflected in operations	A reconciliation of income taxes computed using the U.S. federal statutory rate of 21% to that reflected in the consolidated statements of operations are as follows (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Year Ended December 31, ​ 2020 2019 2018 Income tax benefit using U.S. federal statutory rate ​ $ 22,861 ​ $ 4,517 ​ $ (59,297) ​ Permanent differences ​ 74 ​ 65 ​ 218 ​ State income taxes, net of federal benefit ​ 7,565 ​ (1,902) ​ (17,121) ​ Disallowed Separation related costs ​ ​ — ​ ​ 4,658 ​ ​ — ​ Executive compensation - Section 162(m) ​ ​ 1,718 ​ ​ 662 ​ ​ 8 ​ Meals and entertainment ​ ​ 395 ​ ​ 495 ​ ​ 995 ​ Non-deductible share-based compensation ​ (144) ​ (1,202) ​ (494) ​ Excess tax benefits ​ ​ 5,132 ​ ​ 3,324 ​ ​ (1,223) ​ Fair market valuation of Note Hedge Warrants and Convertible Note Hedges ​ ​ 1,680 ​ ​ (290) ​ ​ 2,367 ​ Tax credits ​ (3,149) ​ (4,374) ​ (7,863) ​ Expiring net operating losses and tax credits ​ 1,991 ​ 3,764 ​ 250 ​ Effect of change in state tax rate on deferred tax assets and deferred tax liabilities ​ (208) ​ (2,563) ​ 1,476 ​ Change in the valuation allowance ​ (35,230) ​ (7,154) ​ 80,684 ​ Income tax expense ​ $ 2,685 ​ $ — ​ $ — ​
Schedule of components of deferred tax assets and liabilities	Deferred tax assets and liabilities were determined based on the difference between financial statement and tax bases using enacted tax rates in effect for the year in which the differences are expected to reverse. The components of the Company’s deferred tax assets and liabilities are as follows (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, ​ 2020 2019 Deferred tax assets: ​ ​ ​ ​ ​ ​ ​ Net operating loss carryforwards ​ $ 234,772 ​ $ 265,494 ​ Tax credit carryforwards ​ 60,607 ​ 59,892 ​ Capitalized research and development ​ 7,498 ​ 9,952 ​ Share-based compensation ​ ​ 21,848 ​ ​ 24,401 ​ Basis difference on collaboration agreement for North America with AbbVie ​ ​ 62,629 ​ ​ 48,594 ​ Accruals and reserves ​ ​ 6,114 ​ ​ 6,415 ​ Basis difference on 2022 Convertible Notes ​ ​ 6,183 ​ ​ 4,322 ​ Interest expense ​ ​ 3,386 ​ ​ 22,020 ​ Operating lease liability ​ ​ 6,504 ​ ​ 6,421 ​ Other ​ 5,049 ​ 5,295 ​ Total deferred tax assets ​ 414,590 ​ 452,806 ​ Deferred tax liabilities: ​ ​ ​ ​ ​ ​ ​ Basis difference on 2024 Convertible Notes ​ ​ (5,951) ​ ​ (7,381) ​ Basis difference on 2026 Convertible Notes ​ ​ (9,022) ​ ​ (10,276) ​ Operating lease right-of-use assets ​ ​ (4,603) ​ ​ (4,905) ​ Total deferred tax liabilities ​ ​ (19,576) ​ ​ (22,562) ​ Net deferred tax asset ​ ​ 395,014 ​ ​ 430,244 ​ Valuation allowance ​ (395,014) ​ (430,244) ​ Net deferred tax asset ​ $ — ​ $ — ​
Summary of changes in the unrecognized tax benefits	The following table summarizes the changes in the Company’s unrecognized income tax benefits for the years ended December 31, 2020, 2019, and 2018 (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Year Ended December 31, ​ ​ ​ 2020 ​ 2019 ​ 2018 ​ Balance at the beginning of the period ​ $ 53,099 ​ $ 38,551 ​ $ 24,078 ​ Increases based on tax positions related to the current period ​ ​ 66,687 ​ ​ 51,699 ​ ​ 38,551 ​ Increases for tax positions related to prior periods ​ ​ — ​ ​ 1,400 ​ ​ — ​ Decreases for tax positions in prior periods ​ ​ (51,699) ​ ​ (38,551) ​ ​ (24,078) ​ Balance at the end of the period ​ $ 68,087 ​ $ 53,099 ​ $ 38,551 ​

Selected Quarterly Financial _2

Selected Quarterly Financial Data (Unaudited) (Tables)	12 Months Ended
	Dec. 31, 2020
Table Text Blocks
Selected Quarterly Financial Data (Unaudited)	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ First ​ Second ​ Third ​ Fourth ​ Total ​ ​ Quarter ​ Quarter ​ Quarter ​ Quarter ​ Year ​ ​ (in thousands, except per share data) 2020 ​ ​ ​ ​ ​ Total revenues (1) ​ $ 79,943 ​ $ 89,432 ​ $ 103,468 ​ $ 116,680 ​ $ 389,523 ​ Total cost and expenses (2) ​ 66,716 ​ 56,719 ​ 57,852 ​ 65,296 ​ 246,583 ​ Other expense, net (3) ​ (9,882) ​ (7,509) ​ (9,804) ​ (6,884) ​ (34,079) ​ Net income and comprehensive income ​ 3,345 ​ 25,204 ​ 34,423 ​ 43,204 ​ 106,176 ​ Net income per share—basic ​ ​ 0.02 ​ ​ 0.16 ​ ​ 0.22 ​ ​ 0.27 ​ ​ 0.67 ​ Net income per share—diluted ​ ​ 0.02 ​ ​ 0.16 ​ ​ 0.21 ​ ​ 0.27 ​ ​ 0.66 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ First ​ Second ​ Third ​ Fourth ​ Total ​ ​ Quarter ​ Quarter ​ Quarter ​ Quarter ​ Year ​ ​ (in thousands, except per share data) 2019 ​ ​ ​ ​ ​ Total revenues (4) ​ $ 68,730 ​ $ 102,215 ​ $ 131,167 ​ $ 126,301 ​ $ 428,413 ​ Total cost and expenses (5) ​ 85,663 ​ 80,638 ​ 65,280 ​ 76,709 ​ 308,290 ​ Other expense, net (6) ​ (4,912) ​ (9,294) ​ (45,239) ​ (1,735) ​ (61,180) ​ Net (loss) income from continuing operations ​ ​ (21,846) ​ ​ 12,283 ​ ​ 20,648 ​ ​ 47,858 ​ 58,943 ​ Net loss from discontinued operations (7) ​ ​ (37,438) ​ ​ — ​ ​ — ​ ​ — ​ (37,438) ​ Net income (loss) and comprehensive income (loss) ​ (59,284) ​ 12,283 ​ 20,648 ​ 47,858 ​ 21,505 ​ Income per share from continuing operations, net of income taxes—basic ​ $ (0.14) ​ $ 0.08 ​ $ 0.13 ​ $ 0.31 ​ $ 0.38 ​ Income per share from continuing operations, net of income taxes—diluted ​ ​ (0.14) ​ ​ 0.08 ​ ​ 0.13 ​ ​ 0.30 ​ ​ 0.38 ​ Net loss per share from discontinued operations—basic and diluted ​ ​ (0.24) ​ ​ — ​ ​ — ​ ​ — ​ ​ (0.24) ​ Net income (loss) per share—basic ​ ​ (0.38) ​ ​ 0.08 ​ ​ 0.13 ​ ​ 0.31 ​ ​ 0.14 ​ Net income (loss) per share—diluted ​ ​ (0.38) ​ ​ 0.08 ​ ​ 0.13 ​ ​ 0.30 ​ ​ 0.14 ​ (1) Total revenues includes approximately $8.0 million of revenue from sales of linaclotide API to the Company’s linaclotide partners for the year ended December 31, 2020. (2) Total costs and expenses includes approximately $15.4 million in restructuring expenses for the year ended December 31, 2020. (3) Other expense, net includes approximately $6.1 million loss on fair value remeasurement of derivatives for the year ended December 31, 2020. (4) Total revenues includes approximately $48.8 million of revenue from sales of linaclotide API to the Company’s linaclotide partners, primarily driven by the commercialization of linaclotide in Japan for the year ended December 31, 2019, as well as approximately $32.4 million related to the non-contingent payments from the Amended AstraZeneca Agreement and a $10.0 million upfront fee from the Amended Astellas License Agreement, both executed during the third quarter of 2019. (5) Total costs and expenses includes approximately $3.6 million in restructuring expenses for the year ended December 31, 2019, as well as approximately $3.2 million related to the gain on lease modification in April 2019. (6) Other expense, net includes approximately $31.0 million in loss on extinguishment of debt related to the partial repurchase of the 2022 Convertible Notes and the redemption of the 2026 Notes, and approximately $3.0 million gain on fair value remeasurement of derivatives for the year ended December 31, 2019. (7) During the year ended December 31, 2019, the Company completed the Separation. Certain amounts related to Cyclerion have been reclassified as discontinued operations for the year ended December 31, 2019.

Nature of Business - Workforce

Nature of Business - Workforce Reduction and Restructuring (Details)	1 Months Ended
	Sep. 30, 2020employee
Reduction in Workforce, Discontinued Development of IW-3718, September 29, 2020
Workforce Reduction
Number of employees expected to be eliminated	100

Nature of Business - Accumulate

Nature of Business - Accumulated Deficit (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Accumulated deficit
Net income	$ 43,204	$ 34,423	$ 25,204	$ 3,345	$ 47,858	$ 20,648	$ 12,283	$ (59,284)	$ 106,176	$ 21,505	$ (282,368)
Accumulated deficit since inception	$ 1,466,056				$ 1,572,232				$ 1,466,056	$ 1,572,232

Summary of Significant Accoun_4

Summary of Significant Accounting Policies - Segment Information (Details) - segment	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Segment information
Number of reportable segments	1	1	1

Summary of Significant Accoun_5

Summary of Significant Accounting Policies - Cash and Cash Equivalents (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Cash and Cash Equivalents
Cash Equivalent included in cash and cash equivalent	$ 349	$ 177

Summary of Significant Accoun_6

Summary of Significant Accounting Policies - Restricted Cash (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Restricted Cash [Abstract]
Restricted cash	$ 2,220	$ 2,221	$ 7,676
Restricted cash, current	1,735	1,250
Restricted cash, noncurrent	$ 485	$ 971

Summary of Significant Accoun_7

Summary of Significant Accounting Policies - Concentrations of Credit Risk (Details)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Accounts Receivable | Credit Concentration Risk | AbbVie
Concentrations
Concentration risk percentage (as a percent)	76.00%	90.00%
Accounts Receivable | Credit Concentration Risk | Astellas Pharma Inc.
Concentrations
Concentration risk percentage (as a percent)	1.00%	8.00%
Revenue from Contract with Customer Benchmark | Customer Concentration Risk | AbbVie
Concentrations
Concentration risk percentage (as a percent)	96.00%	78.00%	77.00%
Revenue from Contract with Customer Benchmark | Customer Concentration Risk | Astellas Pharma Inc.
Concentrations
Concentration risk percentage (as a percent)	1.00%	13.00%	20.00%

Summary of Significant Accoun_8

Summary of Significant Accounting Policies - Property and Equipment (Details)	12 Months Ended
	Dec. 31, 2020
Laboratory equipment
Property and Equipment
Estimated useful life	5 years
Computer and office equipment
Property and Equipment
Estimated useful life	3 years
Furniture and fixtures
Property and Equipment
Estimated useful life	7 years
Software
Property and Equipment
Estimated useful life	3 years

Summary of Significant Accoun_9

Summary of Significant Accounting Policies - Finite Lived Intangible Assets (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2018USD ($)
Finite Lived Intangible Assets
Impairment of intangible assets	$ 151,794

Summary of Significant Accou_10

Summary of Significant Accounting Policies - Leases (Details)	12 Months Ended
	Dec. 31, 2020
Leases
Lease, Practical Expedients, Package	true
Lease, Practical Expedient, Lessor Single Lease Component	true

Summary of Significant Accou_11

Summary of Significant Accounting Policies - Derivative Assets and Liabilities (Details) - Convertible Senior Notes	Sep. 16, 2019	Aug. 12, 2019	Jun. 30, 2015
2.25% Convertible Senior Notes due 2022
Notes Payable
Stated interest rate (as a percent)	2.25%		2.25%
0.75% Convertible Senior Notes due 2024
Notes Payable
Stated interest rate (as a percent)		0.75%
1.50% Convertible Senior Notes due 2026
Notes Payable
Stated interest rate (as a percent)		1.50%

Summary of Significant Accou_12

Summary of Significant Accounting Policies - Revenue Recognition - General Information (Details)	12 Months Ended
	Dec. 31, 2020
U.S. | AbbVie
Collaboration agreements
Percentage of the pre-tax net profit or loss (as a percent)	50.00%

Summary of Significant Accou_13

Summary of Significant Accounting Policies - Revenue Recognition - Practical Expedients (Details)	12 Months Ended
	Dec. 31, 2020
Practical expedients
Practical Expedient, Incremental Cost	true

Summary of Significant Accou_14

Summary of Significant Accounting Policies - Patent Costs (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Patent Costs
Selling, general and administrative	$ 140,003	$ 172,450	$ 219,676
Patents
Patent Costs
Selling, general and administrative	$ 2,300	$ 7,800	$ 5,000

Summary of Significant Accou_15

Summary of Significant Accounting Policies - New Accounting Pronouncements (Details)	12 Months Ended
	Dec. 31, 2020
Accounting Standards Update 2016-02
New Accounting Pronouncements
Change in Accounting Principle, Accounting Standards Update, Adopted	true
Change in Accounting Principle, Accounting Standards Update, Adoption Date	Jan. 1, 2019
Change in Accounting Principle, Accounting Standards Update, Transition Option Elected	us-gaap:AccountingStandardsUpdate201602CumulativeEffectPeriodOfAdoptionMember
Accounting Standards Update 2016-13
New Accounting Pronouncements
Change in Accounting Principle, Accounting Standards Update, Adopted	true
Change in Accounting Principle, Accounting Standards Update, Adoption Date	Jan. 1, 2020
Change in Accounting Principle, Accounting Standards Update, Early Adoption	false
Accounting Standards Update 2017-04
New Accounting Pronouncements
Change in Accounting Principle, Accounting Standards Update, Adopted	true
Change in Accounting Principle, Accounting Standards Update, Adoption Date	Jan. 1, 2020
Change in Accounting Principle, Accounting Standards Update, Early Adoption	false
Accounting Standards Update 2018-13
New Accounting Pronouncements
Change in Accounting Principle, Accounting Standards Update, Adopted	true
Change in Accounting Principle, Accounting Standards Update, Adoption Date	Jan. 1, 2020
Change in Accounting Principle, Accounting Standards Update, Early Adoption	false
Accounting Standards Update 2018-15
New Accounting Pronouncements
Change in Accounting Principle, Accounting Standards Update, Adopted	true
Change in Accounting Principle, Accounting Standards Update, Adoption Date	Jan. 1, 2020
Change in Accounting Principle, Accounting Standards Update, Early Adoption	false
Change in Accounting Principle, Accounting Standards Update, Transition Option Elected	us-gaap:AccountingStandardsUpdate201815ProspectiveMember
Accounting Standards Update 2018-17
New Accounting Pronouncements
Change in Accounting Principle, Accounting Standards Update, Adopted	true
Change in Accounting Principle, Accounting Standards Update, Adoption Date	Jan. 1, 2020
Change in Accounting Principle, Accounting Standards Update, Early Adoption	false
Accounting Standards Update 2019-12
New Accounting Pronouncements
Change in Accounting Principle, Accounting Standards Update, Adopted	false
Change in Accounting Principle, Accounting Standards Update, Early Adoption	false
Accounting Standards Update 2020-06
New Accounting Pronouncements
Change in Accounting Principle, Accounting Standards Update, Adopted	false
Change in Accounting Principle, Accounting Standards Update, Early Adoption	false

Cyclerion Separation - Separati

Cyclerion Separation - Separation Agreement (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019	Apr. 01, 2019
Assets:
Prepaid expenses and other current assets	$ 9,189	$ 10,685
Property and equipment, net	8,929	12,429
Other assets	943	790
Total assets	559,238	402,748
Liabilities:
Accrued research and development costs	1,898	2,956
Accrued expenses and other current liabilities	$ 26,486	$ 30,465
Cyclerion Therapeutics, Inc.
Assets:
Prepaid expenses and other current assets			$ 1,169
Property and equipment, net			10,241
Other assets			21
Total assets			11,431
Liabilities:
Accrued research and development costs			5,673
Accrued expenses and other current liabilities			3,149
Total liabilities			8,822
Net Assets Transferred to Cyclerion			$ 2,609

Cyclerion Separation - Related

Cyclerion Separation - Related Party Information (Details) - Affiliated Entity - Cyclerion Therapeutics, Inc. $ in Millions	12 Months Ended
	Dec. 31, 2020USD ($)agreement	Dec. 31, 2019USD ($)
Cyclerion Separation
Tenant improvement reimbursement provisions received		$ 1.3
Incremental stock-based compensation expense		0
Transition services agreements | agreement	2
Other income for services provided to related party		0.3
Accounts payable due related party		1.5
Research and development
Cyclerion Separation
Expense for service provided by related party	$ 2.3	$ 4.5

Cyclerion Separation - Summary

Cyclerion Separation - Summary of Expenses (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2019	Dec. 31, 2019	Dec. 31, 2018
Net Loss from Discontinued Operations
Net loss from discontinued operations	$ 37,438	$ 37,438	$ 88,222
sGC Business | Discontinued Operations, Disposed of by Means Other than Sale, Spinoff
Net Loss from Discontinued Operations
Net loss from discontinued operations		37,438	88,222
Research and development | sGC Business | Discontinued Operations, Disposed of by Means Other than Sale, Spinoff
Net Loss from Discontinued Operations
Net loss from discontinued operations		21,792	65,443
Selling, general and administrative | sGC Business | Discontinued Operations, Disposed of by Means Other than Sale, Spinoff
Net Loss from Discontinued Operations
Net loss from discontinued operations		$ 15,646	21,615
Restructuring expenses | sGC Business | Discontinued Operations, Disposed of by Means Other than Sale, Spinoff
Net Loss from Discontinued Operations
Net loss from discontinued operations			$ 1,164

Cyclerion Separation - Summar_2

Cyclerion Separation - Summary of Assets and Liabilities Held for Disposition (Details) - Discontinued Operations, Disposed of by Means Other than Sale, Spinoff - sGC Business - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Assets:
Assets	$ 0	$ 0
Liabilities:
Liabilities	$ 0	$ 0

Net Income (Loss) Per Share - C

Net Income (Loss) Per Share - Computation (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Numerator:
Net income (loss)	$ 43,204	$ 34,423	$ 25,204	$ 3,345	$ 47,858	$ 20,648	$ 12,283	$ (59,284)	$ 106,176	$ 21,505	$ (282,368)
Net income (loss) available to common stockholders, basic									106,176	21,505	(282,368)
Net income (loss) available to common stockholders, diluted									$ 106,176	$ 21,505	$ (282,368)
Denominator:
Weighted average number of common shares outstanding used in net income (loss) per share - basic (in shares)									159,427	156,023	152,634
Effect of dilutive securities:
Weighted average number of common shares outstanding used in net income (loss) per share - diluted (in shares)									160,655	156,023	152,634
Net income (loss) per share - basic (in dollars per share)	$ 0.27	$ 0.22	$ 0.16	$ 0.02	$ 0.31	$ 0.13	$ 0.08	$ (0.38)	$ 0.67	$ 0.14	$ (1.85)
Net income (loss) per share - diluted (in dollars per share)	$ 0.27	$ 0.21	$ 0.16	$ 0.02	$ 0.30	$ 0.13	$ 0.08	$ (0.38)	$ 0.66	$ 0.14	$ (1.85)
Stock options
Effect of dilutive securities:
Effect of dilutive securities									367
Time-based Restricted Stock Units
Effect of dilutive securities:
Effect of dilutive securities									766
Performance-based Restricted Stock Units
Effect of dilutive securities:
Effect of dilutive securities									1
Restricted Stock
Effect of dilutive securities:
Effect of dilutive securities									94

Net Income (Loss) Per Share - P

Net Income (Loss) Per Share - Potentially Dilutive Securities (Details) - shares shares in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Potentially dilutive securities
Total potentially dilutive securities excluded from the computation of diluted weighted average shares outstanding (in shares)	58,554	67,087	64,080
Stock options
Potentially dilutive securities
Total potentially dilutive securities excluded from the computation of diluted weighted average shares outstanding (in shares)	11,746	17,194	20,457
Restricted Stock
Potentially dilutive securities
Total potentially dilutive securities excluded from the computation of diluted weighted average shares outstanding (in shares)	2	182	65
Time-based Restricted Stock Units
Potentially dilutive securities
Total potentially dilutive securities excluded from the computation of diluted weighted average shares outstanding (in shares)	209	3,207	3,058
Performance-based Restricted Stock Units
Potentially dilutive securities
Total potentially dilutive securities excluded from the computation of diluted weighted average shares outstanding (in shares)	93
Note Hedge Warrants
Potentially dilutive securities
Total potentially dilutive securities excluded from the computation of diluted weighted average shares outstanding (in shares)	8,318	8,318	20,250
2.25% Convertible Senior Notes due 2022
Potentially dilutive securities
Total potentially dilutive securities excluded from the computation of diluted weighted average shares outstanding (in shares)	8,318	8,318	20,250
0.75% Convertible Senior Notes due 2024
Potentially dilutive securities
Total potentially dilutive securities excluded from the computation of diluted weighted average shares outstanding (in shares)	14,934	14,934
1.50% Convertible Senior Notes due 2026
Potentially dilutive securities
Total potentially dilutive securities excluded from the computation of diluted weighted average shares outstanding (in shares)	14,934	14,934

Goodwill and Intangible Assets

Goodwill and Intangible Assets - Intangible Assets - General Information (Details) - Developed Technology - USD ($) $ in Millions	Jul. 31, 2018	Jun. 02, 2016
DUZALLO
Goodwill and Intangible Assets
Intangible assets, net		$ 145.1
Accumulated amortization	$ 11.7
ZURAMPIC
Goodwill and Intangible Assets
Intangible assets, net		$ 22
Accumulated amortization	$ 3.6

Goodwill and Intangible Asset_2

Goodwill and Intangible Assets - Intangible Assets - Impairment (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2018USD ($)
Goodwill and Intangible Assets
Impairment of intangible assets	$ 151,794
Developed Technology
Goodwill and Intangible Assets
Impairment of intangible assets	$ 151,800

Goodwill and Intangible Asset_3

Goodwill and Intangible Assets - Goodwill Impairment (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Goodwill
Impairment of goodwill	$ 0	$ 0	$ 0

Collaboration, License, Promo_3

Collaboration, License, Promotion and Other Commercial Agreements - Summary (Details) - USD ($) $ in Thousands	Aug. 01, 2019	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Revenues:
Revenue		$ 116,680	$ 103,468	$ 89,432	$ 79,943	$ 126,301	$ 131,167	$ 102,215	$ 68,730	$ 389,523	$ 428,413	$ 346,639
Collaborative arrangements revenue
Revenues:
Revenue										381,545	379,652	272,839
Collaborative arrangement, other agreements
Revenues:
Revenue										1,335	1,845	1,226
Sale of active pharmaceutical ingredient
Revenues:
Revenue										7,978	48,761	70,355
AbbVie | Collaborative arrangement, promotion agreements
Revenues:
Revenue											3,723	4,290
AbbVie | Sale of active pharmaceutical ingredient
Revenues:
Revenue										421		756
AbbVie | North America | Collaborative arrangements revenue
Revenues:
Revenue										370,902	327,591	266,177
AbbVie | North America | Collaborative arrangement, collaboration and license agreements
Revenues:
Revenue										370,902	327,591	266,177
AbbVie | Europe and Other | Collaborative arrangement, collaboration and license agreements
Revenues:
Revenue										2,196	1,718	1,146
AstraZeneca | Collaborative arrangement, collaboration and license agreements
Revenues:
Revenue										682	32,628
AstraZeneca | Sale of active pharmaceutical ingredient
Revenues:
Revenue										5,540	2,973
Astellas Pharma Inc. | Collaborative arrangement, collaboration and license agreements
Revenues:
Revenue	$ 20,400									2,128	10,147
Astellas Pharma Inc. | Sale of active pharmaceutical ingredient
Revenues:
Revenue										2,017	45,788	$ 69,599
Alnylam | Collaborative arrangement, promotion agreements
Revenues:
Revenue										$ 4,302	$ 2,000

Collaboration, License, Promo_4

Collaboration, License, Promotion and Other Commercial Agreements - Accounts Receivable (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Accounts receivable, net
Accounts receivable, net	$ 145.8	$ 43.9
Accounts receivable, net of accounts payable	110.9
AbbVie
Accounts receivable, net
Accounts payable	$ 4.3

Collaboration, License, Promo_5

Collaboration, License, Promotion and Other Commercial Agreements - Related Party Transactions (Details) $ in Thousands	Dec. 31, 2019USD ($)
Related party transactions
Related party accounts receivable, net of related party accounts payable	$ 105,967
Related party accounts payable, net	1,509
Investor | Allergan
Related party transactions
Related party accounts receivable, net	110,100
Related party accounts payable, net	$ 4,100

Collaboration, License, Promo_6

Collaboration, License, Promotion and Other Commercial Agreements - Deferred Revenue (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Deferred revenue
Deferred revenue	$ 0	$ 900

Collaboration, License, Promo_7

Collaboration, License, Promotion and Other Commercial Agreements - North America - General Information (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2020USD ($)itempayment	Dec. 31, 2019USD ($)	Dec. 31, 2018USD ($)
Collaboration, License, Promotion and Other Commercial Agreements
Research and development expense	$ 88,062	$ 115,044	$ 101,060
Sales milestones
Collaboration, License, Promotion and Other Commercial Agreements
Sales-related milestone if certain conditions are met	80,000
AbbVie
Collaboration, License, Promotion and Other Commercial Agreements
Equity investment in the entity's capital stock	$ 25,000
Remaining commercial-period performance obligations | item	3
Cost sharing amount, reduction to research and development	$ 5,600	7,200	9,000
Collaborative arrangement, percentage of obligation of development costs incurred	50.00%
Percentage of net profit from commercialization (as a percent)	50.00%
Percentage of net loss from commercialization (as a percent)	50.00%
AbbVie | Development and sales milestones
Collaboration, License, Promotion and Other Commercial Agreements
Cumulative license fees and development milestone payments received	$ 205,000
AbbVie | Development milestones
Collaboration, License, Promotion and Other Commercial Agreements
Number of milestone payments received | payment	6
North America
Collaboration, License, Promotion and Other Commercial Agreements
Research and development expense	$ 20,100	$ 37,600	$ 39,200

Collaboration, License, Promo_8

Collaboration, License, Promotion and Other Commercial Agreements - North America - Change in Accounting Estimate (Details) - USD ($) $ in Thousands	3 Months Ended										12 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Change in accounting estimate
Revenue	$ 116,680	$ 103,468	$ 89,432	$ 79,943	$ 126,301	$ 131,167	$ 102,215	$ 68,730			$ 389,523	$ 428,413	$ 346,639
Collaborative arrangements revenue
Change in accounting estimate
Revenue											381,545	379,652	272,839
Collaborative arrangements revenue | AbbVie | North America
Change in accounting estimate
Revenue											370,902	327,591	266,177
Collaborative arrangements, LINZESS | AbbVie | North America
Change in accounting estimate
Revenue											$ 368,603	$ 325,429	$ 264,243
Sales Returns and Allowances | Collaborative arrangements, LINZESS | AbbVie | North America | Collaborative arrangement, collaboration and license agreements
Change in accounting estimate
Revenue										$ (29,700)
Sales Returns and Allowances | AbbVie
Change in accounting estimate
Revenue									$ 200	$ 59,300

Collaboration, License, Promo_9

Collaboration, License, Promotion and Other Commercial Agreements - North America - Collaborative Arrangements Revenue (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Revenues:
Revenue	$ 116,680	$ 103,468	$ 89,432	$ 79,943	$ 126,301	$ 131,167	$ 102,215	$ 68,730	$ 389,523	$ 428,413	$ 346,639
Collaborative arrangements revenue
Revenues:
Revenue									381,545	379,652	272,839
AbbVie | North America | Collaborative arrangements revenue
Revenues:
Revenue									370,902	327,591	266,177
AbbVie | North America | Collaborative arrangements, LINZESS
Revenues:
Revenue									368,603	325,429	264,243
AbbVie | North America | Royalty
Revenues:
Revenue									$ 2,299	$ 2,162	$ 1,934

Collaboration, License, Prom_10

Collaboration, License, Promotion and Other Commercial Agreements - North America - Commercial Efforts (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Collaboration, License, Promotion and Other Commercial Agreements
Revenue	$ 116,680	$ 103,468	$ 89,432	$ 79,943	$ 126,301	$ 131,167	$ 102,215	$ 68,730	$ 389,523	$ 428,413	$ 346,639
Selling, general and administrative costs incurred by the Company									(140,003)	(172,450)	(219,676)
AbbVie | U.S.
Collaboration, License, Promotion and Other Commercial Agreements
Patent prosecution costs										2,400
Patent litigation costs									600	2,200
Collaborative arrangements revenue
Collaboration, License, Promotion and Other Commercial Agreements
Revenue									381,545	379,652	272,839
Collaborative arrangements, LINZESS | AbbVie | U.S.
Collaboration, License, Promotion and Other Commercial Agreements
Revenue									368,603	325,429	264,243
Selling, general and administrative costs incurred by the Company									(39,312)	(38,123)	(42,435)
The Company's share of net profit									$ 329,291	$ 287,306	$ 221,808

Collaboration, License, Prom_11

Collaboration, License, Promotion and Other Commercial Agreements - North America - Royalty Revenue (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Revenues:
Revenue	$ 116,680	$ 103,468	$ 89,432	$ 79,943	$ 126,301	$ 131,167	$ 102,215	$ 68,730	$ 389,523	$ 428,413	$ 346,639
Collaborative arrangements revenue
Revenues:
Revenue									381,545	379,652	272,839
Collaborative arrangements revenue | North America | AbbVie
Revenues:
Revenue									370,902	327,591	266,177
Royalty | North America | AbbVie
Revenues:
Revenue									2,299	2,162	1,934
Royalty | Canada and Mexico | AbbVie
Revenues:
Revenue									$ 2,300	$ 2,200	$ 1,900

Collaboration, License, Prom_12

Collaboration, License, Promotion and Other Commercial Agreements - European and Other Territories (Details) - USD ($) $ in Thousands

3 Months Ended

12 Months Ended

Dec. 31, 2020

Sep. 30, 2020

Jun. 30, 2020

Mar. 31, 2020

Dec. 31, 2019

Sep. 30, 2019

Jun. 30, 2019

Mar. 31, 2019

Dec. 31, 2020

Dec. 31, 2019

Dec. 31, 2018

Oct. 31, 2015

Sep. 30, 2012

Collaboration, License, Promotion and Other Commercial Agreements

Revenue

$ 116,680

$ 103,468

$ 89,432

$ 79,943

$ 126,301

$ 131,167

$ 102,215

$ 68,730

$ 389,523

$ 428,413

$ 346,639

Collaborative arrangements revenue

Collaboration, License, Promotion and Other Commercial Agreements

Revenue

$ 381,545

379,652

272,839

License | AbbVie

Collaboration, License, Promotion and Other Commercial Agreements

Royalty percentage, five years following the first commercial sale

upper-single digits

Annual royalty

5 years

Royalty percentage, thereafter

low-double digits

Royalty percentage, expanded territory

lower-single digits

License | AbbVie | Europe

Collaboration, License, Promotion and Other Commercial Agreements

Remaining milestone payment due upon the amendment to the license agreement

$ 42,500

Revenue remaining performance obligation

$ 0

Royalty | AbbVie | Europe

Collaboration, License, Promotion and Other Commercial Agreements

Revenue

$ 2,200

$ 1,700

$ 1,100

Collaboration, License, Prom_13

Collaboration, License, Promotion and Other Commercial Agreements - Japan (Details) $ in Thousands

Aug. 01, 2019USD ($)

Nov. 30, 2009USD ($)payment

Dec. 31, 2020USD ($)

Sep. 30, 2020USD ($)

Jun. 30, 2020USD ($)

Mar. 31, 2020USD ($)

Dec. 31, 2019USD ($)

Sep. 30, 2019USD ($)

Jun. 30, 2019USD ($)

Mar. 31, 2019USD ($)

Dec. 31, 2020USD ($)

Dec. 31, 2019USD ($)

Dec. 31, 2018USD ($)

Dec. 31, 2017USD ($)

Collaboration, License, Promotion and Other Commercial Agreements

Revenue

$ 116,680

$ 103,468

$ 89,432

$ 79,943

$ 126,301

$ 131,167

$ 102,215

$ 68,730

$ 389,523

$ 428,413

$ 346,639

Astellas Pharma Inc., 2009 License Agreement | Japan

Collaboration, License, Promotion and Other Commercial Agreements

Up-front fee received

$ 30,000

Number of milestone payments | payment

3

Milestone payments received

$ 45,000

Collaborative arrangements revenue

Collaboration, License, Promotion and Other Commercial Agreements

Revenue

381,545

379,652

272,839

Collaborative arrangement, collaboration and license agreements | Astellas Pharma Inc.

Collaboration, License, Promotion and Other Commercial Agreements

Revenue

$ 20,400

2,128

10,147

Collaborative arrangement, collaboration and license agreements | Astellas Pharma Inc. | Japan

Collaboration, License, Promotion and Other Commercial Agreements

Non-refundable upfront payment

$ 10,000

Collaborative arrangement, collaboration and license agreements, upfront fee | Astellas Pharma Inc.

Collaboration, License, Promotion and Other Commercial Agreements

Revenue

10,000

Sale of active pharmaceutical ingredient

Collaboration, License, Promotion and Other Commercial Agreements

Revenue

7,978

48,761

70,355

Sale of active pharmaceutical ingredient | Astellas Pharma Inc.

Collaboration, License, Promotion and Other Commercial Agreements

Revenue

2,017

45,788

$ 69,599

Sale of active pharmaceutical ingredient | Astellas Pharma Inc. | Japan

Collaboration, License, Promotion and Other Commercial Agreements

Revenue remaining performance obligation

$ 0

Sale of active pharmaceutical ingredient | Astellas Pharma Inc., 2009 License Agreement

Collaboration, License, Promotion and Other Commercial Agreements

Revenue

27,500

Sale of active pharmaceutical ingredient | Astellas Pharma Inc., 2009 License Agreement, Amended 2019

Collaboration, License, Promotion and Other Commercial Agreements

Revenue

2,000

$ 18,300

Royalty | Astellas Pharma Inc., 2009 License Agreement, Amended 2019

Collaboration, License, Promotion and Other Commercial Agreements

Revenue

$ 2,100

Collaboration, License, Prom_14

Collaboration, License, Promotion and Other Commercial Agreements - China, Hong Kong and Macau (Details) $ in Thousands

1 Months Ended

3 Months Ended

12 Months Ended

Jan. 31, 2021USD ($)

Dec. 31, 2020USD ($)

Sep. 30, 2020USD ($)

Jun. 30, 2020USD ($)

Mar. 31, 2020USD ($)

Dec. 31, 2019USD ($)

Sep. 30, 2019USD ($)

Jun. 30, 2019USD ($)

Mar. 31, 2019USD ($)

Dec. 31, 2020USD ($)installment

Dec. 31, 2019USD ($)

Dec. 31, 2018USD ($)

Collaboration, License, Promotion and Other Commercial Agreements

Revenue

$ 116,680

$ 103,468

$ 89,432

$ 79,943

$ 126,301

$ 131,167

$ 102,215

$ 68,730

$ 389,523

$ 428,413

$ 346,639

Collaborative arrangements revenue

Collaboration, License, Promotion and Other Commercial Agreements

Revenue

381,545

379,652

272,839

Sale of active pharmaceutical ingredient

Collaboration, License, Promotion and Other Commercial Agreements

Revenue

7,978

48,761

70,355

AstraZeneca | Collaborative arrangement, collaboration and license agreements

Collaboration, License, Promotion and Other Commercial Agreements

Revenue

682

32,628

AstraZeneca | Sale of active pharmaceutical ingredient

Collaboration, License, Promotion and Other Commercial Agreements

Revenue

$ 5,540

2,973

AstraZeneca | China, Hong Kong, and Macau

Collaboration, License, Promotion and Other Commercial Agreements

Percentage of net loss from commercialization (as a percent)

55.00%

Pre-launch commercial services and supply chain services

1,200

$ 900

AstraZeneca | China, Hong Kong, and Macau | Collaborative arrangements revenue

Collaboration, License, Promotion and Other Commercial Agreements

Collaborative arrangement, significant financing component, transaction price

2,600

$ 2,600

Collaborative arrangement, expected interest income

$ 2,600

2,600

AstraZeneca | China, Hong Kong, and Macau | Collaborative arrangement, collaboration agreements

Collaboration, License, Promotion and Other Commercial Agreements

Milestone payment to be received by company upon milestone achievement

90,000

Amount of non-contingent arrangement consideration

$ 35,000

Non-contingent consideration installments | installment

3

Percentage of tiered royalties

20.00%

AstraZeneca | China, Hong Kong, and Macau | Collaborative arrangement, transition services agreement

Collaboration, License, Promotion and Other Commercial Agreements

Regulatory and administrative services initial term

2 years

AstraZeneca | China, Hong Kong, and Macau | Subsequent Event | Collaborative arrangement, collaboration agreements

Collaboration, License, Promotion and Other Commercial Agreements

Non-contingent arrangement consideration installment received

$ 10,000

AstraZeneca License Agreement | Collaborative arrangement, collaboration and license agreements

Collaboration, License, Promotion and Other Commercial Agreements

Revenue

$ 700

32,600

AstraZeneca License Agreement | Collaborative arrangement, collaboration agreements

Collaboration, License, Promotion and Other Commercial Agreements

Revenue

32,400

32,400

AstraZeneca License Agreement | Collaborative arrangement, transition services agreement

Collaboration, License, Promotion and Other Commercial Agreements

Revenue

600

$ 200

AstraZeneca License Agreement | Royalty

Collaboration, License, Promotion and Other Commercial Agreements

Revenue

$ 100

Collaboration, License, Prom_15

Collaboration, License, Promotion and Other Commercial Agreements - Promotion Agreements (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Collaboration, License, Promotion and Other Commercial Agreements
Revenue	$ 116,680	$ 103,468	$ 89,432	$ 79,943	$ 126,301	$ 131,167	$ 102,215	$ 68,730	$ 389,523	$ 428,413	$ 346,639
Deferred revenue	0				900				0	900
Collaborative arrangements revenue
Collaboration, License, Promotion and Other Commercial Agreements
Revenue									381,545	379,652	$ 272,839
Alnylam | Collaborative arrangement, promotion agreements
Collaboration, License, Promotion and Other Commercial Agreements
Total annual service fees due	5,500								5,500
Revenue									3,500	2,000
Deferred revenue	$ 0				$ 900				0	900
Alnylam | Royalty
Collaboration, License, Promotion and Other Commercial Agreements
Revenue									$ 800	$ 0

Fair Value of Financial Instr_3

Fair Value of Financial Instruments - General Information (Details)	Dec. 31, 2020
Fair Value of Financial Instruments
Threshold percentage of collateralized value (as a percent)	102.00%

Fair Value of Financial Instr_4

Fair Value of Financial Instruments - Measured on Recurring Basis (Details) - Recurring basis - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Assets:
Convertible note hedges	$ 13,065	$ 31,366
Total assets measured at fair value	364,300	210,577
Liabilities:
Note hedge warrants	12,088	24,260
Total liabilities measured at fair value	12,088	24,260
Money market funds
Assets:
Cash and cash equivalents	349,014	139,190
Restricted cash	2,221	2,221
Repurchase agreements
Assets:
Cash and cash equivalents		37,800
Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets:
Total assets measured at fair value	351,235	179,211
Quoted Prices in Active Markets for Identical Assets (Level 1) | Money market funds
Assets:
Cash and cash equivalents	349,014	139,190
Restricted cash	2,221	2,221
Quoted Prices in Active Markets for Identical Assets (Level 1) | Repurchase agreements
Assets:
Cash and cash equivalents		37,800
Significant Unobservable Inputs (Level 3)
Assets:
Convertible note hedges	13,065	31,366
Total assets measured at fair value	13,065	31,366
Liabilities:
Note hedge warrants	12,088	24,260
Total liabilities measured at fair value	$ 12,088	$ 24,260

Fair Value of Financial Instr_5

Fair Value of Financial Instruments - Transfers Between Fair Value Measurement Levels (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Fair value transfers
Fair value transfer between measurement levels	$ 0	$ 0

Fair Value of Financial Instr_6

Fair Value of Financial Instruments - Assumptions - Convertible Note Hedges (Details)	Dec. 31, 2020$ / sharesY	Dec. 31, 2019$ / sharesY
Fair Value of Financial Instruments
Derivative asset, valuation technique	us-gaap:ValuationTechniqueOptionPricingModelMember	us-gaap:ValuationTechniqueOptionPricingModelMember
Measurement Input, Risk Free Interest Rate
Fair Value of Financial Instruments
Derivative asset, measurement input	0.001	0.016
Measurement Input, Expected Term
Fair Value of Financial Instruments
Derivative asset, measurement input | Y	1.5	2.5
Measurement Input, Share Price
Fair Value of Financial Instruments
Derivative asset, measurement input	11.39	13.31
Measurement Input, Exercise Price
Fair Value of Financial Instruments
Derivative asset, measurement input	14.51	14.51
Measurement Input, Price Volatility
Fair Value of Financial Instruments
Derivative asset, measurement input	0.467	0.491
Measurement Input, Expected Dividend Rate
Fair Value of Financial Instruments
Derivative asset, measurement input	0	0

Fair Value of Financial Instr_7

Fair Value of Financial Instruments - Assumptions - Note Hedge Warrants (Details)	Dec. 31, 2020$ / sharesY	Dec. 31, 2019Y$ / shares
Fair Value of Financial Instruments
Derivative liability, valuation technique	us-gaap:ValuationTechniqueOptionPricingModelMember	us-gaap:ValuationTechniqueOptionPricingModelMember
Measurement Input, Risk Free Interest Rate
Fair Value of Financial Instruments
Derivative liability, measurement input	0.001	0.016
Measurement Input, Expected Term
Fair Value of Financial Instruments
Derivative liability, measurement input | Y	2	3
Measurement Input, Share Price
Fair Value of Financial Instruments
Derivative liability, measurement input	11.39	13.31
Measurement Input, Exercise Price
Fair Value of Financial Instruments
Derivative liability, measurement input	18.82	18.82
Measurement Input, Price Volatility
Fair Value of Financial Instruments
Derivative liability, measurement input	0.503	0.465
Measurement Input, Expected Dividend Rate
Fair Value of Financial Instruments
Derivative liability, measurement input	0	0

Fair Value of Financial Instr_8

Fair Value of Financial Instruments - Change in Level 3 - Convertible Note Hedges (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Change in Level 3 Assets
Balance at beginning of period	$ 31,366	$ 41,020
Cash settlement (received) upon early termination of derivatives		(28,909)
Change in fair value, recorded as a component of (loss) gain on derivatives	(18,301)	19,255
Balance at end of period	$ 13,065	$ 31,366

Fair Value of Financial Instr_9

Fair Value of Financial Instruments - Change in Level 3 - Note Hedge Warrants (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Change in Level 3 Liabilities
Balance at beginning of period	$ (24,260)	$ (33,763)
Cash settlement paid upon early termination of derivatives		25,735
Change in fair value, recorded as a component of gain (loss) on derivatives	12,172	(16,232)
Balance at end of period	$ (12,088)	$ (24,260)

Fair Value of Financial Inst_10

Fair Value of Financial Instruments - Notes Payable (Details) - Convertible Senior Notes - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019	Aug. 31, 2019	Jun. 30, 2015
2.25% Convertible Senior Notes due 2022
Fair value disclosures
Debt redeemed/repurchased			$ 215,000
Aggregate principal amount of notes issued	$ 120,699	$ 120,699		$ 335,700
2.25% Convertible Senior Notes due 2022 | Significant Other Observable Inputs (Level 2)
Fair value disclosures
Estimated fair value	130,200	141,300
0.75% Convertible Senior Notes due 2024
Fair value disclosures
Aggregate principal amount of notes issued	200,000	200,000	200,000
0.75% Convertible Senior Notes due 2024 | Significant Other Observable Inputs (Level 2)
Fair value disclosures
Estimated fair value	222,300	235,700
1.50% Convertible Senior Notes due 2026
Fair value disclosures
Aggregate principal amount of notes issued	200,000	200,000	$ 200,000
1.50% Convertible Senior Notes due 2026 | Significant Other Observable Inputs (Level 2)
Fair value disclosures
Estimated fair value	$ 224,100	$ 240,100

Fair Value of Financial Inst_11

Fair Value of Financial Instruments - Capped Calls with Respect to 2024 Convertible Notes and 2026 Convertible Notes (Details) - Capped Calls with Respect to 2024 Convertible Notes and 2026 Convertible Notes	1 Months Ended
	Aug. 31, 2019$ / shares$ / itemshares
Capped Calls
Number of shares covered by capped calls (in shares) | shares	29,867,480
Strike price (in dollars per share) | $ / shares	$ 13.39
Cap price | $ / item	17.05

Leases - General Information (D

Leases - General Information (Details) - Accounting Standards Update 2016-02	12 Months Ended
	Dec. 31, 2020
New Accounting Pronouncements
Change in Accounting Principle, Accounting Standards Update, Adopted	true
Change in Accounting Principle, Accounting Standards Update, Adoption Date	Jan. 1, 2019
Change in Accounting Principle, Accounting Standards Update, Transition Option Elected	us-gaap:AccountingStandardsUpdate201602CumulativeEffectPeriodOfAdoptionMember

Leases - Lease Cost - Tabular D

Leases - Lease Cost - Tabular Disclosure (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Lease cost
Operating lease cost during period	$ 2,530	$ 16,452
Variable lease payments		1,526
Short-term lease cost	1,420	1,512
Total lease cost	$ 3,950	$ 19,490

Leases - Lease Cost - Sublease

Leases - Lease Cost - Sublease Income (Details) $ in Millions	12 Months Ended
	Dec. 31, 2019USD ($)
Lease cost
Sublease income	$ 0.3

Leases - Operating Leases - Sup

Leases - Operating Leases - Supplemental Cash Flow Information (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Operating leases
Right-of-use assets obtained in exchange for new operating lease upon adoption of ASC 842		$ 88,299
Adjustment to right-of-use assets as a result of the lease modification upon Separation		(40,427)
Adjustment to right-of-use assets as a result of the termination of the Binney Street Lease		(34,440)
Right-of-use assets obtained in exchange for new operating lease liabilities upon execution of Summer Street Lease		18,452
Cash paid for amounts included in the measurement of lease liabilities	$ 1,146	$ 18,598
Weighted-average remaining lease term of operating leases (in years)	9 years 3 months 18 days	10 years 2 months 12 days
Weighted-average discount rate of operating leases (as a percent)	5.80%	5.80%

Leases - Operating Leases - Fut

Leases - Operating Leases - Future Minimum Lease Payments (Details) $ in Thousands	Dec. 31, 2020USD ($)
Future minimum lease payments
2021	$ 3,128
2022	3,129
2023	3,065
2024	3,126
2025	3,189
2026 and thereafter	14,856
Total future minimum lease payments	$ 30,493

Leases - Operating Leases - Ope

Leases - Operating Leases - Operating Lease Obligations (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Operating lease obligations
Total future minimum lease payments	$ 30,493
Less: present value adjustment	(7,047)
Operating lease liabilities	23,446
Less: current portion of operating lease liabilities	(3,128)	$ (1,146)
Operating lease liabilities, net of current portion	$ 20,318	$ 22,082

Leases - Operating Leases - Sum

Leases - Operating Leases - Summer Street Lease (Details) ft² in Thousands, $ in Thousands	Jun. 11, 2019ft²	Dec. 31, 2020USD ($)	Dec. 31, 2019USD ($)
Operating leases
Restricted cash, noncurrent		$ 485	$ 971
Weighted-average discount rate of operating leases (as a percent)		5.80%	5.80%
Operating lease right-of-use assets		$ 16,576	$ 17,743
Operating lease liability		23,446
Asset retirement obligation			486
Operating lease cost		2,530	16,452
Summer Street Lease
Operating leases
Option to extend the term of the lease	true
Rentable area leased (in square feet) | ft²	39
Operating lease, renewal term	5 years
Annual rent escalation (as a percent)	2.00%
Restricted cash, noncurrent		$ 1,000
Weighted-average discount rate of operating leases (as a percent)		5.80%
Operating lease right-of-use assets		$ 16,600	17,700
Operating lease cost		2,500	1,500
Lease liability, net of tenant improvement allowance reimbursement		$ 23,200	$ 22,800

Leases - Operating Leases - Bin

Leases - Operating Leases - Binney Street Lease (Details) $ in Thousands	Jun. 11, 2019USD ($)ft²	Apr. 01, 2019ft²	Dec. 31, 2020USD ($)	Dec. 31, 2019USD ($)	Dec. 31, 2018USD ($)	Jan. 01, 2019USD ($)
Operating leases
Weighted-average discount rate of operating leases (as a percent)			5.80%	5.80%
Operating lease cost			$ 2,530	$ 16,452
Sublease income				300
Restricted cash, noncurrent			485	971
Operating lease right-of-use assets			16,576	17,743
Operating lease liability			$ 23,446
Binney Street Lease
Operating leases
Rentable area leased (in square feet) | ft²	108,000	108,000
Surrendered space (in square feet) | ft²		114,000
Weighted-average discount rate of operating leases (as a percent)	4.00%	5.10%
Gain on modification of lease				3,200
Lease termination cost	$ 9,000
Operating lease cost				16,300
Sublease income				$ 300
Operating lease right-of-use assets						$ 87,700
Rent expense					$ 10,000
Operating lease liability						$ 94,300

Leases - Operating Leases - Veh

Leases - Operating Leases - Vehicle Fleet Leases (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Apr. 30, 2018
Operating leases
Restricted cash, current	$ 1,735	$ 1,250
Operating lease cost	2,530	16,452
Vehicles, 2018 Vehicle Leases
Operating leases
Operating lease, term				12 months
Operating lease, renewal term				1 month
Restricted cash, current	1,300	1,300
Operating lease cost	$ 1,400	$ 1,500
Rent expenses			$ 800

Property and Equipment - Tabula

Property and Equipment - Tabular Disclosure (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Property and Equipment
Property and equipment, gross	$ 20,734	$ 22,511
Less accumulated depreciation and amortization	(11,805)	(10,082)
Property and equipment, net	8,929	12,429
Software
Property and Equipment
Property and equipment, gross	8,615	9,568
Leasehold improvements
Property and Equipment
Property and equipment, gross	7,407	7,318
Laboratory equipment
Property and Equipment
Property and equipment, gross	1,898	2,193
Furniture and fixtures
Property and Equipment
Property and equipment, gross	1,517	1,508
Computer and office equipment
Property and Equipment
Property and equipment, gross	$ 1,297	1,293
Construction in process
Property and Equipment
Property and equipment, gross		$ 631

Property and Equipment - Expens

Property and Equipment - Expenses (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Property and Equipment
Depreciation and amortization	$ 2.3	$ 5.6	$ 3.9

Property and Equipment - Restru

Property and Equipment - Restructuring (Details) $ in Millions	12 Months Ended
	Dec. 31, 2020USD ($)
Reduction in Workforce, Discontinued Development of IW-3718, September 29, 2020
Impairment of Long-Lived Assets
Impairment of long-lived assets	$ 1.2

Accrued Expenses and Other Cu_3

Accrued Expenses and Other Current Liabilities - Tabular Disclosure (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Accrued Expenses
Accrued incentive compensation	$ 8,719	$ 11,760
Accrued vacation	2,625	2,540
Professional fees	530	1,421
Salaries	627	2,973
Other employee benefits	1,442	1,260
Restructuring liabilities	10,510	179
Other	2,033	10,332
Total accrued expenses and other current liabilities	$ 26,486	$ 30,465

Accrued Expenses and Other Cu_4

Accrued Expenses and Other Current Liabilities - Additional Information (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Accrued Expenses
Other accrued expenses	$ 2,033	$ 10,332
Other accrued liabilities, uninvoiced vendor liabilities	300
Other accrued expenses, goods received but not yet invoiced		4,100
Other accrued expenses, move activities		900
Other accrued expenses, unbilled inventories		600
Accrued interest	$ 1,600	300
Other accrued expenses, equipment for clinical studies		$ 200

Notes Payable - 8.375% Notes Du

Notes Payable - 8.375% Notes Due 2026 (Details) - USD ($) $ in Thousands	Sep. 23, 2016	Dec. 31, 2019	Dec. 31, 2020	Sep. 16, 2019	Aug. 31, 2019
Notes Payable
Debt issuance costs capitalized			$ 6,543
Loss on extinguishment of debt		$ 30,977
8.375% Notes due 2026 | Notes Payable
Notes Payable
Stated interest rate (as a percent)	8.375%		8.375%
Aggregate principal amount of notes issued	$ 150,000
Net proceed received	11,200
Debt issuance costs capitalized	$ 500
Debt redeemed/repurchased					$ 116,500
Debt redemption/repurchase price				$ 123,000
Loss on extinguishment of debt		$ 7,600
Percentage of net sales to determine quarterly payments (as a percent)	7.50%

Notes Payable - Convertible Sen

Notes Payable - Convertible Senior Notes - General Information (Details)	Aug. 31, 2019USD ($)	Apr. 15, 2019USD ($)$ / sharesshares	Aug. 31, 2019USD ($)	Jun. 30, 2015USD ($)D$ / sharesshares	Dec. 31, 2020USD ($)$ / sharesshares	Dec. 31, 2019USD ($)	Sep. 16, 2019
Notes Payable
Payments for convertible note hedges			$ 25,200,000	$ 21,100,000
Net proceeds received						$ 400,000,000
Proceeds from partial termination of convertible note hedges and note hedge warrants			3,200,000			3,174,000
Loss on extinguishment of debt						30,977,000
Equity component of convertible senior notes						92,502,000
Convertible Note Hedge
Notes Payable
Conversion price (in dollars per share) | $ / shares		$ 14.51			$ 16.58
Shares issuable upon conversion of debt (in shares) | shares					20,249,665
2.25% Convertible Senior Notes due 2022 | Note Hedge Warrants
Notes Payable
Shares issuable upon conversion of debt (in shares) | shares		23,135,435
2.25% Convertible Senior Notes due 2022 | Convertible Senior Notes
Notes Payable
Aggregate principal amount of notes issued				335,700,000	$ 120,699,000	$ 120,699,000
Net proceed received				324,000,000
Fees and expenses				$ 11,700,000
Stated interest rate (as a percent)				2.25%			2.25%
Conversion rate, number of shares to be issued per		68.9172		60.3209
Principal amount used for debt instrument conversion ratio		$ 1,000		$ 1,000
Conversion price (in dollars per share) | $ / shares		$ 14.51		$ 16.58
Shares issuable upon conversion of debt (in shares) | shares		23,135,435		20,249,665
Number of trading days | D				20
Consecutive trading days | D				30
Minimum percentage of stock price				130.00%
Number of business days immediately after any five consecutive trading day period during the measurement period | D				5
Number of consecutive trading days before five business days during the measurement period | D				5
Repurchase price, as percentage of principal amount, if company undergoes change of control				100.00%
Maximum period of the sole remedy for event failures in the Indenture					180 days
Amortization period				7 years
Debt redeemed/repurchased	$ 215,000,000		215,000,000
Debt redemption/repurchase price	227,300,000		227,300,000
Loss on extinguishment of debt	$ 23,400,000		23,400,000
Equity component of convertible senior notes			27,000,000
Initial debt issuance costs			$ 2,800,000
2.25% Convertible Senior Notes due 2022 | Convertible Senior Notes | Minimum
Notes Payable
Percentage of aggregate principal amount payable, in case of event of default				25.00%
2.25% Convertible Senior Notes due 2022 | Convertible Senior Notes | Maximum
Notes Payable
Percentage of the trading price to the product of the sale price of the entity's common stock and the conversion rate				98.00%

Notes Payable - Convertible S_2

Notes Payable - Convertible Senior Notes - Balances (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019	Aug. 31, 2019	Jun. 30, 2015
Liability component:
Long-term Debt, Gross	$ 546,523
Less: unamortized debt discount	(83,900)
Less: unamortized debt issuance costs	(6,543)
Net carrying amount	430,256
Convertible Senior Notes
Liability component:
Less: unamortized debt discount	(83,900)	$ (104,700)
Less: unamortized debt issuance costs	(6,543)	(8,005)
Net carrying amount	430,256	407,994
Total equity component	112,309	112,309
2.25% Convertible Senior Notes due 2022 | Convertible Senior Notes
Liability component:
Aggregate principal amount of notes issued	120,699	120,699		$ 335,700
Total equity component	19,807	19,807
0.75% Convertible Senior Notes due 2024 | Convertible Senior Notes
Liability component:
Aggregate principal amount of notes issued	200,000	200,000	$ 200,000
Total equity component	41,152	41,152
1.50% Convertible Senior Notes due 2026 | Convertible Senior Notes
Liability component:
Aggregate principal amount of notes issued	200,000	200,000	$ 200,000
Total equity component	$ 51,350	$ 51,350

Notes Payable - Convertible S_3

Notes Payable - Convertible Senior Notes - Additional Information (Details) - 2.25% Convertible Senior Notes due 2022 - Convertible Senior Notes - USD ($) $ in Millions	1 Months Ended
	Jun. 30, 2015	Dec. 31, 2020	Jun. 30, 2019
Notes Payable
Debt issuance costs incurred	$ 11.7
Debt issuance costs allocated to equity components	4
Debt issuance costs allocated to liability components	$ 7.7
Debt instrument term	7 years
Effective interest rate on liability components		9.70%	9.34%

Notes Payable - Convertible S_4

Notes Payable - Convertible Senior Notes - Total Interest Expense (Details) - 2.25% Convertible Senior Notes due 2022 - Convertible Senior Notes - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Interest Expense
Contractual interest expense	$ 7,216	$ 7,361	$ 7,553
Amortization of debt issuance costs	1,462	1,190	971
Amortization of debt discount	20,800	17,683	15,437
Total interest expense	$ 29,478	$ 26,234	$ 23,961

Notes Payable - Convertible S_5

Notes Payable - Convertible Senior Notes - Future Minimum Payments (Details) $ in Thousands	Dec. 31, 2020USD ($)
Future minimum payments of Convertible senior notes
2021	$ 7,216
2022	126,557
2023	4,500
2024	203,750
2025	3,000
2026	201,500
Total future minimum payments under the convertible senior notes	546,523
Less: amounts representing interest	(25,824)
Less: unamortized debt discount	(83,900)
Less: unamortized debt issuance costs	(6,543)
Net carrying amount	$ 430,256

Notes Payable - 0.75% Convertib

Notes Payable - 0.75% Convertible Senior Notes Due 2024 and 1.50% Convertible Senior Notes Due 2026 (Details)	Aug. 12, 2019	Aug. 07, 2019USD ($)$ / shares	Apr. 15, 2019USD ($)$ / sharesshares	Aug. 31, 2019USD ($)D	Jun. 30, 2015USD ($)D$ / sharesshares	Dec. 31, 2020USD ($)	Dec. 31, 2019USD ($)	Sep. 16, 2019
Notes Payable
Payments for convertible note hedges				$ 25,200,000	$ 21,100,000
Repurchase price				100.00%
Percentage of aggregate principal amount of notes outstanding and payable in case of event of default under the agreement				25.00%
2.25% Convertible Senior Notes due 2022 | Convertible Senior Notes
Notes Payable
Aggregate principal amount of notes issued					335,700,000	$ 120,699,000	$ 120,699,000
Net proceed received					324,000,000
Fees and expenses					$ 11,700,000
Stated interest rate (as a percent)					2.25%			2.25%
Conversion rate, number of shares to be issued per			68.9172		60.3209
Principal amount used for debt instrument conversion ratio			$ 1,000		$ 1,000
Initial conversion price (in dollars per share) | $ / shares			$ 14.51		$ 16.58
Shares issuable upon conversion of debt (in shares) | shares			23,135,435		20,249,665
Number of trading days | D					20
Consecutive trading days | D					30
Minimum percentage of stock price					130.00%
Number of business days immediately after any five consecutive trading day period during the measurement period | D					5
Number of consecutive trading days before five business days during the measurement period | D					5
Repurchase price, as percentage of principal amount, if company undergoes change of control					100.00%
Amortization period					7 years
2.25% Convertible Senior Notes due 2022 | Convertible Senior Notes | Minimum
Notes Payable
Percentage of aggregate principal amount payable, in case of event of default					25.00%
2.25% Convertible Senior Notes due 2022 | Convertible Senior Notes | Maximum
Notes Payable
Percentage of the trading price to the product of the sale price of the entity's common stock and the conversion rate					98.00%
0.75% Convertible Senior Notes due 2024 and 1.50% Convertible Senior Notes due 2026 | Convertible Senior Notes
Notes Payable
Net proceed received				$ 391,000,000
Fees and expenses				9,000,000
Conversion rate, number of shares to be issued per	74.6687
Principal amount used for debt instrument conversion ratio		$ 1,000		$ 1,000
Initial conversion price (in dollars per share) | $ / shares		$ 13.39
Number of consecutive trading days before five business days during the measurement period | D				5
0.75% Convertible Senior Notes due 2024 and 1.50% Convertible Senior Notes due 2026 | Convertible Senior Notes | Calendar quarter commencing after December 31, 2019
Notes Payable
Number of trading days | D				20
Consecutive trading days | D				30
0.75% Convertible Senior Notes due 2024 and 1.50% Convertible Senior Notes due 2026 | Convertible Senior Notes | Measurement period
Notes Payable
Number of business days immediately after any five consecutive trading day period during the measurement period | D				5
0.75% Convertible Senior Notes due 2024 and 1.50% Convertible Senior Notes due 2026 | Convertible Senior Notes | Minimum | Calendar quarter commencing after December 31, 2019
Notes Payable
Minimum percentage of stock price				130.00%
0.75% Convertible Senior Notes due 2024 and 1.50% Convertible Senior Notes due 2026 | Convertible Senior Notes | Maximum | Measurement period
Notes Payable
Conversion premium percentage on sale price of common stock				98.00%
0.75% Convertible Senior Notes due 2024 | Convertible Senior Notes
Notes Payable
Aggregate principal amount of notes issued				$ 200,000,000		200,000,000	200,000,000
Stated interest rate (as a percent)	0.75%
Amortization period				5 years
1.50% Convertible Senior Notes due 2026 | Convertible Senior Notes
Notes Payable
Aggregate principal amount of notes issued				$ 200,000,000		$ 200,000,000	$ 200,000,000
Stated interest rate (as a percent)	1.50%
Amortization period				7 years

Notes Payable - 2.25% Convertib

Notes Payable - 2.25% Convertible Senior Notes Due 2022, 0.75% Convertible Senior Notes Due 2024 and 1.50% Convertible Senior Notes Due 2026 (Details) - Convertible Senior Notes - USD ($) $ in Millions	1 Months Ended
	Aug. 31, 2019	Jun. 30, 2015	Dec. 31, 2020	Jun. 30, 2019
2.25% Convertible Senior Notes due 2022
Notes Payable
Debt issuance costs incurred		$ 11.7
Debt issuance costs allocated to equity components		4
Debt issuance costs allocated to liability components		$ 7.7
Debt instrument term		7 years
Effective interest rate on liability components			9.70%	9.34%
0.75% Convertible Senior Notes due 2024 and 1.50% Convertible Senior Notes due 2026
Notes Payable
Debt issuance costs incurred	$ 9
Debt issuance costs allocated to equity components	2.1
Debt issuance costs allocated to liability components	$ 6.9
0.75% Convertible Senior Notes due 2024
Notes Payable
Debt instrument term	5 years
Effective interest rate on liability components			6.30%
1.50% Convertible Senior Notes due 2026
Notes Payable
Debt instrument term	7 years
Effective interest rate on liability components			6.60%

Notes Payable - Convertible Not

Notes Payable - Convertible Note Hedge and Warrant Transactions (Details) - USD ($) $ / shares in Units, $ in Thousands	1 Months Ended	12 Months Ended
	Jun. 30, 2015	Dec. 31, 2020	Dec. 31, 2019	Apr. 15, 2019
Notes Payable
Long-term asset		$ 13,065	$ 31,366
Long-term liability		$ 12,088	$ 24,260
Net derivative issuance cost	$ 21,100
Convertible Note Hedge
Notes Payable
Shares issuable upon conversion of debt (in shares)		20,249,665
Conversion price (in dollars per share)		$ 16.58		$ 14.51
Long-term asset	91,900
Note Hedge Warrant Derivatives
Notes Payable
Shares into which warrants may be converted (in shares)		20,249,665
Trading day period		150 days
Long-term liability	$ 70,800
Note Hedge Warrants
Notes Payable
Warrants strike price (in dollars per share)		$ 21.50		$ 18.82

Notes Payable - Capped Calls wi

Notes Payable - Capped Calls with Respect to 2024 Convertible Notes and 2026 Convertible Notes (Details) $ / shares in Units, $ in Thousands	1 Months Ended	12 Months Ended
	Aug. 31, 2019USD ($)$ / shares$ / itemshares	Dec. 31, 2019USD ($)
Capped Calls
Purchase of capped calls		$ 25,159
Equity component of issuance costs for convertible senior notes		$ 2,092
Capped Calls with Respect to 2024 Convertible Notes and 2026 Convertible Notes
Capped Calls
Payment made to enter into Capped Calls	$ 25,200
Strike price (in dollars per share) | $ / shares	$ 13.39
Cap price | $ / item	17.05
Number of shares covered by capped calls (in shares) | shares	29,867,480
Purchase of capped calls	$ 25,000
Equity component of issuance costs for convertible senior notes	$ 200

Commitments and Contingencies -

Commitments and Contingencies - Guarantees (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Indemnification Agreement
Guarantees
Liabilities recorded	$ 0	$ 0

Commitments and Contingencies_2

Commitments and Contingencies - Litigation (Details) $ in Millions	12 Months Ended
	Dec. 31, 2018USD ($)
Mylan
Litigation Settlement [Abstract]
Litigation settlement amount	$ 4

Stockholders' Equity (Details)

Stockholders' Equity (Details)	12 Months Ended
	Dec. 31, 2020Vote
Common stock
Number of voting rights per share	1
Description of the number of voting rights per share	one

Employee Stock Benefit Plans -

Employee Stock Benefit Plans - Summary of Expense Recognized by Share-based Compensation Arrangement (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Employee Stock Benefit Plans
Expense recognized for share-based compensation arrangements	$ 31,175	$ 31,278	$ 41,082
Stock options
Employee Stock Benefit Plans
Expense recognized for share-based compensation arrangements	7,680	12,526	20,478
Time-based Restricted Stock Units
Employee Stock Benefit Plans
Expense recognized for share-based compensation arrangements	18,624	15,488	17,160
Performance-based Restricted Stock Units
Employee Stock Benefit Plans
Expense recognized for share-based compensation arrangements	2,190
Restricted Stock
Employee Stock Benefit Plans
Expense recognized for share-based compensation arrangements	1,886	2,095	2,330
Employee Stock Purchase Plan
Employee Stock Benefit Plans
Expense recognized for share-based compensation arrangements	722	1,115	1,097
Stock awards
Employee Stock Benefit Plans
Expense recognized for share-based compensation arrangements	$ 73	$ 54	$ 17

Employee Stock Benefit Plans _2

Employee Stock Benefit Plans - Share-based Compensation Reflected in the Consolidated Statement of Operations (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Employee Stock Benefit Plans
Share-based compensation expense	$ 31,175	$ 31,278	$ 41,082
Research and development
Employee Stock Benefit Plans
Share-based compensation expense	5,569	6,343	11,500
Selling, general and administrative
Employee Stock Benefit Plans
Share-based compensation expense	23,825	24,281	27,440
Restructuring expenses
Employee Stock Benefit Plans
Share-based compensation expense	$ 1,781	$ 654	$ 2,142

Employee Stock Benefit Plans _3

Employee Stock Benefit Plans - Separation (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Employee Stock Benefit Plans
Share-based compensation expense	$ 31,175	$ 31,278	$ 41,082
Employee Stock Purchase Plan
Employee Stock Benefit Plans
Share-based compensation expense	$ 722	1,115	$ 1,097
Spin-off | Share-based Payment Awards, Excluding Employee Stock Purchase Plan
Employee Stock Benefit Plans
Share-based compensation expense		0
Spin-off | Employee Stock Purchase Plan
Employee Stock Benefit Plans
Share-based compensation expense		$ 300

Employee Stock Benefit Plans _4

Employee Stock Benefit Plans - Share-based Compensation Expense (Details) $ in Millions	12 Months Ended
	Dec. 31, 2019USD ($)
Employee Stock Benefit Plans
Share-based compensation expense, other modifications	$ 3

Employee Stock Benefit Plans _5

Employee Stock Benefit Plans - Stock Benefit Plans (Details) - shares	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2010
2010 Plan | Employee Stock Purchase Plan
Stock Benefit Plans
Purchase price as a percentage of fair market value of a share of common stock on the first or last day of an offering period (as a percent)		85.00%
Offering period		6 months
Shares reserved for issuance (in shares)		400,000
Threshold number of additional shares available for future grant (in shares)	1,000,000
Shares available for future grant (in shares)	4,705,393
2010 Plan | Employee Stock Purchase Plan | Class A common stock
Stock Benefit Plans
Percentage for the threshold number of additional shares available for future grant, expressed as percentage of common stock outstanding on the last day of the immediately preceding fiscal year (as a percent)	1.00%
2019 Equity plan
Stock Benefit Plans
Shares available for future grant (in shares)	9,651,783
2019 Equity plan | Class A common stock
Stock Benefit Plans
Shares reserved for issuance (in shares)	10,000,000
2005 Equity Plan
Stock Benefit Plans
Shares available for future grant (in shares)	0
2019 Equity Plan and 2010 Purchase Plan
Stock Benefit Plans
Shares available for future grant (in shares)	14,357,176

Employee Stock Benefit Plans _6

Employee Stock Benefit Plans - Restricted Stock Awards - Activity (Details) - Restricted Stock - $ / shares	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Number of Shares
Outstanding at the beginning of the period (in shares)	181,648
Granted (in shares)	246,500
Vested and released (in shares)	(181,648)
Outstanding at the end of the period (in shares)	246,500	181,648
Weighted-Average Grant Date Fair Value
Outstanding at the beginning of the period (in dollars per share)	$ 10.76
Granted (in dollars per share)	10.16	$ 10.96	$ 18.58
Vested and released (in dollars per share)	10.46
Outstanding at the end of the period (in dollars per share)	$ 10.38	$ 10.76

Employee Stock Benefit Plans _7

Employee Stock Benefit Plans - Restricted Stock Awards - Weighted-average Grant Date Fair Value (Details) - $ / shares	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Restricted Stock
Weighted-Average Grant Date Fair Value
Weighted-average grant date fair value (in dollars per share)	$ 10.16	$ 10.96	$ 18.58

Employee Stock Benefit Plans _8

Employee Stock Benefit Plans - Restricted Stock Units (Details)	12 Months Ended
	Dec. 31, 2018shares
Restricted Stock Units
Stock Benefit Plans
Right to number of shares of common stock per RSU (in shares)	1

Employee Stock Benefit Plans _9

Employee Stock Benefit Plans - Time-based RSUs - Vesting (Details) - Time-based Restricted Stock Units	12 Months Ended
	Dec. 31, 2020
Minimum
Stock Benefit Plans
Vesting period	2 years
Maximum
Stock Benefit Plans
Vesting period	4 years

Employee Stock Benefit Plans_10

Employee Stock Benefit Plans - Time-based RSUs - Activity (Details) - Time-based Restricted Stock Units - $ / shares	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Number of Shares
Outstanding at the beginning of the period (in shares)	3,207,089
Granted (in shares)	2,708,200
Vested and released (in shares)	(965,625)
Forfeited (in shares)	(779,038)
Outstanding at the end of the period (in shares)	4,170,626	3,207,089
Weighted-Average Grant Date Fair Value
Outstanding at the beginning of the period (in dollars per share)	$ 12.33
Granted (in dollars per share)	11.59	$ 12.11	$ 15.63
Vested and released (in dollars per share)	12.37
Forfeited (in dollars per share)	11.96
Outstanding at the end of the period (in dollars per share)	$ 11.90	$ 12.33

Employee Stock Benefit Plans_11

Employee Stock Benefit Plans - Time-based RSUs - Weighted-average Grant Date Fair Value (Details) - $ / shares	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Time-based Restricted Stock Units
Weighted-Average Grant Date Fair Value
Weighted-average grant date fair value (in dollars per share)	$ 11.59	$ 12.11	$ 15.63

Employee Stock Benefit Plans_12

Employee Stock Benefit Plans - Performance-based RSUs - Vesting (Details) - Performance-based Restricted Stock Units	12 Months Ended
	Dec. 31, 2020
Share-based Payment Arrangement, Tranche One
Stock Benefit Plans
Vesting period	2 years
Share-based Payment Arrangement, Tranche Two
Stock Benefit Plans
Vesting period	3 years

Employee Stock Benefit Plans_13

Employee Stock Benefit Plans - Performance-based RSUs - Assumptions (Details) - Performance-based Restricted Stock Units	12 Months Ended
	Dec. 31, 2020$ / shares
Weighted-average assumptions used to estimate fair value
Fair value of common stock (in dollars per share)	$ 11.78
Expected volatility (as a percent)	53.30%
Expected term	2 years 9 months 18 days
Risk-free interest rate (as a percent)	1.00%
Expected dividend yield (as a percent)	0.00%

Employee Stock Benefit Plans_14

Employee Stock Benefit Plans - Performance-based RSUs - Activity (Details) - Performance-based Restricted Stock Units	12 Months Ended
	Dec. 31, 2020$ / sharesshares
Number of Shares
Outstanding at the beginning of the period (in shares) | shares	0
Granted (in shares) | shares	586,157
Outstanding at the end of the period (in shares) | shares	586,157
Weighted-Average Grant Date Fair Value
Outstanding at the beginning of the period (in dollars per share) | $ / shares	$ 0
Granted (in dollars per share) | $ / shares	12.48
Outstanding at the end of the period (in dollars per share) | $ / shares	$ 12.48

Employee Stock Benefit Plans_15

Employee Stock Benefit Plans - Performance-based RSUs - Weighted-average Grant Date Fair Value (Details)	12 Months Ended
	Dec. 31, 2020$ / shares
Performance-based Restricted Stock Units
Weighted-Average Grant Date Fair Value
Weighted-average grant date fair value (in dollars per share)	$ 12.48

Employee Stock Benefit Plans_16

Employee Stock Benefit Plans - Stock Options - General Information (Details)	12 Months Ended
	Dec. 31, 2020
Stock Benefit Plans
Expiration period	10 years
Stock options
Stock Benefit Plans
Vesting period	4 years

Employee Stock Benefit Plans_17

Employee Stock Benefit Plans - Stock Options - Assumptions (Details) - Stock options	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Weighted-average assumptions used to estimate fair value
Expected volatility (as a percent)	46.60%	46.30%	43.70%
Expected term	6 years 1 month 6 days	6 years 1 month 6 days	6 years
Risk-free interest rate (as a percent)	1.50%	2.50%	2.70%
Expected dividend yield (as a percent)	0.00%	0.00%	0.00%

Employee Stock Benefit Plans_18

Employee Stock Benefit Plans - Stock Options - Additional Information (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Stock Benefit Plans
Weighted average grant date fair value (in dollars per share)	$ 5.89	$ 6.10	$ 6.81
Share-based compensation expense	$ 31,175	$ 31,278	$ 41,082
Stock options
Stock Benefit Plans
Share-based compensation expense	$ 7,680	$ 12,526	20,478
Stock options with time-based and performance-based vesting
Stock Benefit Plans
Vested (in shares)	0	0
Share-based compensation expense	$ 0	$ 0	$ 0

Employee Stock Benefit Plans_19

Employee Stock Benefit Plans - Stock Options - Activity (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Number of Shares
Outstanding at the beginning of the period (in shares)	17,194,239
Granted (in shares)	55,000
Exercised (in shares)	(1,735,081)
Cancelled (in shares)	(2,054,487)
Outstanding at the end of the period (in shares)	13,459,671	17,194,239
Weighted-Average Exercise Price
Outstanding at the beginning of the period (in dollars per share)	$ 12.13
Granted (in dollars per share)	12.84
Exercised (in dollars per share)	10.21
Cancelled (in dollars per share)	13
Outstanding at the end of the period (in dollars per share)	$ 12.25	$ 12.13
Vested or expected to vest
Number of Shares (in shares)	13,280,456
Weighted-Average Exercise Price (in dollars per share)	$ 12.26
Weighted Average Contractual Life	4 years 2 months 23 days
Aggregate Intrinsic Value	$ 5,575
Stock options
Weighted Average Contractual Life - Outstanding	4 years 3 months 7 days	5 years 1 month 9 days
Aggregate Intrinsic Value - Outstanding	$ 5,613	$ 25,226
Number of Shares - Exercisable (in shares)	11,963,812
Weighted-Average Exercise Price - Exercisable (in dollars per share)	$ 12.26
Weighted Average Contractual Life - Exercisable	3 years 10 months 24 days
Aggregate Intrinsic Value - Exercisable	$ 5,371

Employee Stock Benefit Plans_20

Employee Stock Benefit Plans - Stock Options - Total Intrinsic Value (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Stock options
Total intrinsic value of options exercised	$ 3.5	$ 5.1	$ 20.1

Employee Stock Benefit Plans_21

Employee Stock Benefit Plans - Unrecognized Share-based Compensation (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2020USD ($)
Stock options with time-based vesting
Unrecognized share-based compensation
Unrecognized expense, net of estimated forfeitures, options	$ 6,557
Weighted-average remaining recognition period	1 year 10 months 2 days
Stock options with time-based and performance-based vesting
Unrecognized share-based compensation
Unrecognized expense, net of estimated forfeitures, options	$ 88
Restricted Stock
Unrecognized share-based compensation
Unrecognized expense, net of estimated forfeitures, other than options	$ 1,473
Weighted-average remaining recognition period	11 months 1 day
Time-based Restricted Stock Units
Unrecognized share-based compensation
Unrecognized expense, net of estimated forfeitures, other than options	$ 26,934
Weighted-average remaining recognition period	2 years 2 months 19 days
Performance-based Restricted Stock Units
Unrecognized share-based compensation
Unrecognized expense, net of estimated forfeitures, other than options	$ 3,291
Weighted-average remaining recognition period	1 year 8 months 12 days

Income Taxes - Income Tax Expen

Income Taxes - Income Tax Expense (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Federal Income Tax Expense (Benefit)
Federal Income Tax Expense (Benefit), Continuing Operations	$ 0	$ 0	$ 0
State Income Tax Expense (Benefit)
Income tax expense related to state income tax	2,700	0	0
Foreign Income Tax Expense (Benefit)
Foreign Income Tax Expense (Benefit), Continuing Operations	0	0	0
Income tax expense	$ 2,685	$ 0	$ 0

Income Taxes - Federal Statutor

Income Taxes - Federal Statutory Rate (Details)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Effective Income Tax Rate Reconciliation, Percent
Federal statutory rate (as a percent)	21.00%	21.00%	21.00%

Income Taxes - Reconciliation o

Income Taxes - Reconciliation of Income Taxes (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Reconciliation of income taxes
Income tax benefit using U.S. federal statutory rate	$ 22,861	$ 4,517	$ (59,297)
Permanent differences	74	65	218
State income taxes, net of federal benefit	7,565	(1,902)	(17,121)
Disallowed separation related costs		4,658
Executive compensation - Section 162(m)	1,718	662	8
Meals and entertainment	395	495	995
Non-deductible share-based compensation	(144)	(1,202)	(494)
Excess tax benefits	5,132	3,324	(1,223)
Fair market valuation of Note Hedge Warrants and Convertible Note Hedges	1,680	(290)	2,367
Tax credits	(3,149)	(4,374)	(7,863)
Expiring net operating losses and tax credits	1,991	3,764	250
Effect of change in state tax rate on deferred tax assets and deferred tax liabilities	(208)	(2,563)	1,476
Change in the valuation allowance	(35,230)	(7,154)	80,684
Income tax expense	$ 2,685	$ 0	$ 0

Income Taxes - Deferred Tax Ass

Income Taxes - Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Deferred tax assets:
Net operating loss carryforwards	$ 234,772	$ 265,494
Tax credit carryforwards	60,607	59,892
Capitalized research and development	7,498	9,952
Share-based compensation	21,848	24,401
Basis difference on collaboration agreement for North America with AbbVie	62,629	48,594
Accruals and reserves	6,114	6,415
Basis difference on 2022 Notes	6,183	4,322
Interest Expense	3,386	22,020
Operating lease liability	6,504	6,421
Other	5,049	5,295
Total deferred tax assets	414,590	452,806
Deferred tax liabilities:
Basis Difference on 2024 Convertible Notes	(5,951)	(7,381)
Basis Difference on 2026 Convertible Notes	(9,022)	(10,276)
Operating lease right-of-use assets	(4,603)	(4,905)
Total deferred tax liabilities	(19,576)	(22,562)
Net deferred tax assets	395,014	430,244
Valuation allowance	(395,014)	(430,244)
Net deferred tax asset	$ 0	$ 0

Income Taxes - Valuation Allowa

Income Taxes - Valuation Allowance (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Income Taxes
Valuation allowance	$ 395,014	$ 430,244
(Decrease) increase in valuation allowance	$ (35,200)	$ (29,100)

Income Taxes - Net Operating Lo

Income Taxes - Net Operating Loss Carryforwards (Details) $ in Billions	Dec. 31, 2020USD ($)
Domestic Tax Authority
Net operating loss carryforwards
Net operating loss carryforwards	$ 1.1
Net operating loss carryforwards, subject to expiration	1
Net operating loss carryforwards, indefinite	0.1
State
Net operating loss carryforwards
Net operating loss carryforwards	$ 0.9

Income Taxes - Tax Credit Carry

Income Taxes - Tax Credit Carryforwards (Details) $ in Millions	Dec. 31, 2020USD ($)
Tax credit carryforward
Tax credit carryforward	$ 65.3

Income Taxes - Unrecognized Inc

Income Taxes - Unrecognized Income Tax Benefits - Tabular Disclosure (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Unrecognized income tax benefits
Unrecognized Tax Benefits, Beginning Balance	$ 53,099	$ 38,551	$ 24,078
Increases based on tax positions related to the current period	66,687	51,699	38,551
Increases for tax positions of prior periods		1,400
Decreases for tax positions in prior periods	(51,699)	(38,551)	(24,078)
Unrecognized Tax Benefits, End Balance	$ 68,087	$ 53,099	$ 38,551

Income Taxes - Unrecognized I_2

Income Taxes - Unrecognized Income Tax Benefits - Additional Information (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Unrecognized tax benefits
Unrecognized tax benefits	$ 68,087	$ 53,099	$ 38,551	$ 24,078
Amount of unrecognized tax benefits that, if recognized, would affect effective tax rate	800
Accrued interest and penalties from uncertain tax positions	$ 0

Defined Contribution Plan (Deta

Defined Contribution Plan (Details) - USD ($)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Defined Contribution Plan
Employer match of first $6,000 of employee contributions (as a percent)	75.00%
Amount of employee contributions matched 75% by employer	$ 6,000
Compensation cost	$ 1,800,000	$ 2,200,000	$ 3,200,000
Minimum
Defined Contribution Plan
Employee contribution per calendar year (as a percent of compensation)	1.00%
Maximum
Defined Contribution Plan
Employee contribution per calendar year (as a percent of compensation)	100.00%

Workforce Reduction and Restr_2

Workforce Reduction and Restructuring - Restructuring Expenses (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Restructuring Expenses
Restructuring expenses	$ 15,382	$ 3,620	$ 14,715

Workforce Reduction and Restr_3

Workforce Reduction and Restructuring - General Information (Details) $ in Thousands	1 Months Ended					12 Months Ended
	Sep. 30, 2020employee	Feb. 28, 2019employee	Aug. 31, 2018employee	Jun. 30, 2018itememployee	Jan. 31, 2018employee	Dec. 31, 2020USD ($)	Dec. 31, 2019USD ($)	Dec. 31, 2018USD ($)
Restructuring Expenses
Restructuring expenses						$ 15,382	$ 3,620	$ 14,715
Restructuring Accruals
Restructuring accruals						10,510	179
Employee severance, benefits and related costs
Restructuring Expenses
Restructuring expenses						11,563	3,198
Restructuring Accruals
Amounts accrued						10,902	75	2,452
Contract related costs
Restructuring Expenses
Restructuring expenses						108
Restructuring Accruals
Amounts accrued						5	104	433
Reduction in Field-based Workforce, January 30, 2018
Workforce Reduction
Number of employees eliminated | employee					60
Restructuring Expenses
Employee severance, benefits and related costs								2,400
Reduction in Headquarter-based Workforce, June 27, 2018
Workforce Reduction
Number of new businesses | item				2
Number of employees expected to be eliminated | employee				40
Restructuring Expenses
Employee severance, benefits and related costs								4,000
Reduction in Headquarter-based Workforce, June 27, 2018 | Employee severance, benefits and related costs
Restructuring Expenses
Restructuring expenses							16
Restructuring Accruals
Amounts accrued							0	696
Reduction in Workforce, Termination of Lesinurad License Agreement, August 16, 2018
Workforce Reduction
Number of employees expected to be eliminated | employee			100
Restructuring Expenses
Restructuring expenses								8,300
Reduction in Workforce, Termination of Lesinurad License Agreement, August 16, 2018 | Employee severance, benefits and related costs
Restructuring Expenses
Restructuring expenses								5,400
Restructuring Accruals
Amounts accrued							0	1,756
Reduction in Workforce, Termination of Lesinurad License Agreement, August 16, 2018 | Contract related costs
Restructuring Expenses
Restructuring expenses						0		2,900
Restructuring Accruals
Amounts accrued						0	104	433
Reduction in Workforce, February 7, 2019
Workforce Reduction
Number of employees expected to be eliminated | employee		35
Restructuring Expenses
Employee severance, benefits and related costs							3,700
Reduction in Workforce, February 7, 2019 | Employee severance, benefits and related costs
Restructuring Expenses
Restructuring expenses						0	3,182
Restructuring Accruals
Amounts accrued						0	75	$ 0
Reduction in Workforce, Discontinued Development of IW-3718, September 29, 2020
Workforce Reduction
Number of employees expected to be eliminated | employee	100
Restructuring Expenses
Restructuring expenses						15,500
Impairment of Long-Lived Assets
Impairment of long-lived assets						1,200
Reduction in Workforce, Discontinued Development of IW-3718, September 29, 2020 | Employee severance, benefits and related costs
Restructuring Expenses
Restructuring expenses						11,563
Restructuring Accruals
Amounts accrued						10,902	0
Reduction in Workforce, Discontinued Development of IW-3718, September 29, 2020 | Contract related costs
Restructuring Expenses
Restructuring expenses						108
Restructuring Accruals
Amounts accrued						$ 5	$ 0

Workforce Reduction and Restr_4

Workforce Reduction and Restructuring - Tabular Disclosure (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Workforce Reduction
Charges	$ 15,382	$ 3,620	$ 14,715
Reduction in Workforce, Termination of Lesinurad License Agreement, August 16, 2018
Workforce Reduction
Charges			8,300
Reduction in Workforce, Discontinued Development of IW-3718, September 29, 2020
Workforce Reduction
Charges	15,500
Employee severance, benefits and related costs
Workforce Reduction
Balance at beginning of period	75	2,452
Charges	11,563	3,198
Amounts paid	(736)	(5,365)
Adjustments		(210)
Balance at end of period	10,902	75	2,452
Employee severance, benefits and related costs | Reduction in Headquarter-based Workforce, June 27, 2018
Workforce Reduction
Balance at beginning of period	0	696
Charges		16
Amounts paid		(689)
Adjustments		(23)
Balance at end of period		0	696
Employee severance, benefits and related costs | Reduction in Workforce, Termination of Lesinurad License Agreement, August 16, 2018
Workforce Reduction
Balance at beginning of period	0	1,756
Charges			5,400
Amounts paid		(1,708)
Adjustments		(48)
Balance at end of period		0	1,756
Employee severance, benefits and related costs | Reduction in Workforce, February 7, 2019
Workforce Reduction
Balance at beginning of period	75	0
Charges	0	3,182
Amounts paid	(75)	(2,968)
Adjustments		(139)
Balance at end of period	0	75	0
Employee severance, benefits and related costs | Reduction in Workforce, Discontinued Development of IW-3718, September 29, 2020
Workforce Reduction
Balance at beginning of period	0
Charges	11,563
Amounts paid	(661)
Balance at end of period	10,902	0
Contract related costs
Workforce Reduction
Balance at beginning of period	104	433
Charges	108
Amounts paid	(103)	(287)
Adjustments	(104)	(42)
Balance at end of period	5	104	433
Contract related costs | Reduction in Workforce, Termination of Lesinurad License Agreement, August 16, 2018
Workforce Reduction
Balance at beginning of period	104	433
Charges	0		2,900
Amounts paid		(287)
Adjustments	(104)	(42)
Balance at end of period	0	104	$ 433
Contract related costs | Reduction in Workforce, Discontinued Development of IW-3718, September 29, 2020
Workforce Reduction
Balance at beginning of period	0
Charges	108
Amounts paid	(103)
Balance at end of period	$ 5	$ 0

Selected Quarterly Financial _3

Selected Quarterly Financial Data (Unaudited) - Tabular Disclosure (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Selected Quarterly Financial Data
Total revenues	$ 116,680	$ 103,468	$ 89,432	$ 79,943	$ 126,301	$ 131,167	$ 102,215	$ 68,730	$ 389,523	$ 428,413	$ 346,639
Total cost and expenses	65,296	57,852	56,719	66,716	76,709	65,280	80,638	85,663	246,583	308,290	497,309
Other expense, net	(6,884)	(9,804)	(7,509)	(9,882)	(1,735)	(45,239)	(9,294)	(4,912)	(34,079)	(61,180)	(43,476)
Net (loss) income from continuing operations					47,858	20,648	12,283	(21,846)	106,176	58,943	(194,146)
Net loss from discontinued operations								(37,438)		(37,438)	(88,222)
Net income (loss)	43,204	34,423	25,204	3,345	47,858	20,648	12,283	(59,284)	106,176	21,505	(282,368)
Comprehensive income (loss)	$ 43,204	$ 34,423	$ 25,204	$ 3,345	$ 47,858	$ 20,648	$ 12,283	$ (59,284)	$ 106,176	$ 21,505	$ (282,289)
Income (loss) per share from continuing operations, net of income taxes - basic (in dollars per share)					$ 0.31	$ 0.13	$ 0.08	$ (0.14)	$ 0.67	$ 0.38	$ (1.27)
Income (loss) per share from continuing operations, net of income taxes - diluted (in dollars per share)					0.30	0.13	0.08	(0.14)	0.66	0.38	(1.27)
Net (loss) income per share from discontinued operations - basic and diluted (in dollars per share)								(0.24)		(0.24)	(0.58)
Net income (loss) per share - basic (in dollars per share)	$ 0.27	$ 0.22	$ 0.16	$ 0.02	0.31	0.13	0.08	(0.38)	0.67	0.14	(1.85)
Net income (loss) per share - diluted (in dollars per share)	$ 0.27	$ 0.21	$ 0.16	$ 0.02	$ 0.30	$ 0.13	$ 0.08	$ (0.38)	$ 0.66	$ 0.14	$ (1.85)

Selected Quarterly Financial _4

Selected Quarterly Financial Data (Unaudited) - Sale of Active Pharmaceutical Ingredient (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Revenues
Revenue	$ 116,680	$ 103,468	$ 89,432	$ 79,943	$ 126,301	$ 131,167	$ 102,215	$ 68,730	$ 389,523	$ 428,413	$ 346,639
AstraZeneca
Revenues
Revenue from non-contingent payments						32,400
Astellas Pharma Inc.
Revenues
Upfront fee received						$ 10,000
Sale of active pharmaceutical ingredient
Revenues
Revenue									7,978	48,761	70,355
Sale of active pharmaceutical ingredient | AstraZeneca
Revenues
Revenue									5,540	2,973
Sale of active pharmaceutical ingredient | Astellas Pharma Inc.
Revenues
Revenue									$ 2,017	$ 45,788	$ 69,599

Selected Quarterly Financial _5

Selected Quarterly Financial Data (Unaudited) - Restructuring Expenses (Details) - USD ($) $ in Thousands	1 Months Ended	12 Months Ended
	Apr. 30, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Restructuring Expenses
Restructuring expenses		$ 15,382	$ 3,620	$ 14,715
Gain on lease modification	$ 3,200		$ 3,169

Selected Quarterly Financial _6

Selected Quarterly Financial Data (Unaudited) - Gain on Lease Modification (Details) - USD ($) $ in Thousands	1 Months Ended	12 Months Ended
	Apr. 30, 2019	Dec. 31, 2019
Selected Quarterly Financial Data
Gain on lease modification	$ 3,200	$ 3,169

Selected Quarterly Financial _7

Selected Quarterly Financial Data (Unaudited) - Gain (Loss) on Derivatives (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Gain (Loss) on Derivatives
Gain (loss) on derivatives	$ (6,129)	$ 3,023	$ (8,743)

Selected Quarterly Financial _8

Selected Quarterly Financial Data (Unaudited) - Loss on Extinguishment of Debt (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2019USD ($)
Notes Payable
Loss on extinguishment of debt	$ 30,977