Cash Equivalents and Marketable Securities - Schedule of Cash Equivalent and Marketable Securities Classified as Available-for-Sale (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Cash And Cash Equivalents [Line Items]
Amortized Cost Basis	$ 488,889	$ 517,256
Unrealized Gains	47	196
Unrealized Losses	(28)	(4)
Estimated Fair Value	488,908	517,448
Money Market Funds
Cash And Cash Equivalents [Line Items]
Amortized Cost Basis Cash Equivalents	69,644	266,437
Total cash equivalents	69,644	266,437
Short-term Marketable Securities
Cash And Cash Equivalents [Line Items]
Amortized Cost Basis	419,245	250,819
Unrealized Gains	47	196
Unrealized Losses	(28)	(4)
Estimated Fair Value	419,264	251,011
Short-term Marketable Securities \| U.S. Treasury Bills
Cash And Cash Equivalents [Line Items]
Amortized Cost Basis		14,996
Unrealized Gains		3
Estimated Fair Value		14,999
Short-term Marketable Securities \| U.S. Treasury Notes
Cash And Cash Equivalents [Line Items]
Amortized Cost Basis	60,526	45,292
Unrealized Gains	29	100
Unrealized Losses		(1)
Estimated Fair Value	60,555	45,391
Short-term Marketable Securities \| Commercial Paper
Cash And Cash Equivalents [Line Items]
Amortized Cost Basis	184,273	144,851
Unrealized Gains	7
Unrealized Losses	(3)
Estimated Fair Value	184,277	144,851
Short-term Marketable Securities \| Corporate Debt Securities
Cash And Cash Equivalents [Line Items]
Amortized Cost Basis	134,365	45,680
Unrealized Gains	10	93
Unrealized Losses	(24)	(3)
Estimated Fair Value	134,351	$ 45,770
Short-term Marketable Securities \| Supranational Debt Securities
Cash And Cash Equivalents [Line Items]
Amortized Cost Basis	40,081
Unrealized Gains	1
Unrealized Losses	(1)
Estimated Fair Value	$ 40,081

Amount, before tax, of unrealized gain in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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Amount, before tax, of unrealized loss in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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

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

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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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Amount of 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. Excludes cash and cash equivalents within disposal group and discontinued operation.

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