Fair Value Measurements - Financial Assets and Liabilities Measured at Fair Value on Recurring Basis (Details) - USD ($) $ in Thousands	Mar. 31, 2022	Dec. 31, 2021
Financial assets:
Equity warrant investment	$ 1,095	$ 1,067
Total financial assets	830,806	875,800
Financial liabilities:
Success payment liabilities	5,635	9,486
Total financial liabilities	5,635	9,486
U.S. Treasury securities
Financial assets:
Marketable securities	310,625	289,706
U.S. government agency securities
Financial assets:
Marketable securities	152,185	93,626
Corporate debt securities
Financial assets:
Marketable securities	263,059	285,156
Money market funds
Financial assets:
Money market funds	103,842	206,245
Level 1
Financial assets:
Equity warrant investment	0	0
Total financial assets	103,842	206,245
Financial liabilities:
Success payment liabilities	0	0
Total financial liabilities	0	0
Level 1 \| U.S. Treasury securities
Financial assets:
Marketable securities	0
Level 1 \| U.S. government agency securities
Financial assets:
Marketable securities	0
Level 1 \| Corporate debt securities
Financial assets:
Marketable securities	0
Level 1 \| Money market funds
Financial assets:
Money market funds	103,842	206,245
Level 2
Financial assets:
Equity warrant investment	0	0
Total financial assets	725,869	668,488
Financial liabilities:
Success payment liabilities	0	0
Total financial liabilities	0	0
Level 2 \| U.S. Treasury securities
Financial assets:
Marketable securities	310,625	289,706
Level 2 \| U.S. government agency securities
Financial assets:
Marketable securities	152,185	93,626
Level 2 \| Corporate debt securities
Financial assets:
Marketable securities	263,059	285,156
Level 2 \| Money market funds
Financial assets:
Money market funds	0	0
Level 3
Financial assets:
Equity warrant investment	1,095	1,067
Total financial assets	1,095	1,067
Financial liabilities:
Success payment liabilities	5,635	9,486
Total financial liabilities	5,635	9,486
Level 3 \| U.S. Treasury securities
Financial assets:
Marketable securities	0	0
Level 3 \| U.S. government agency securities
Financial assets:
Marketable securities	0	0
Level 3 \| Corporate debt securities
Financial assets:
Marketable securities	0	0
Level 3 \| Money market funds
Financial assets:
Money market funds	$ 0	$ 0

Success Payment Liabilities, Fair Value Disclosure

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- Definition

Fair value portion of probable future economic benefits obtained or controlled by an entity as a result of past transactions or events.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (a)
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- Definition

Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03(6))
-URI http://asc.fasb.org/extlink&oid=120398452&loc=d3e534808-122878

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-SubTopic 30
-Section 45
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=124258926&loc=SL82898722-210454

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
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-Section 45
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-Topic 320
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Fair value portion of currency on hand as well as demand deposits with banks or financial institutions. Includes other kinds of accounts that have the general characteristics of demand deposits. Also includes short-term, highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates.

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- Definition

Amount of investment in equity security measured at fair value with change in fair value recognized in net income (FV-NI), classified as current.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 825
-SubTopic 10
-Section 45
-Paragraph 1A
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Fair value of financial obligations, including, but not limited to, debt instruments, derivative liabilities, federal funds purchased and sold under agreements to repurchase, securities loaned or sold under agreements to repurchase, financial instruments sold not yet purchased, guarantees, line of credit, loans and notes payable, servicing liability, and trading liabilities.

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