Cash Equivalents, Restricted Cash and Investments - Amortized Cost and Fair Value of Cash Equivalents and Investments (Detail) - USD ($) $ in Thousands	Mar. 31, 2022	Dec. 31, 2021
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	$ 370,445	$ 354,813
Gross Unrealized Gains	15	7
Gross Unrealized Losses	(1,870)	(490)
Available-for-sale Securities	368,590	354,330
Money Market Fund [Member]
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	37,331	41,960
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	0
Available-for-sale Securities	37,331	41,960
U.S. Treasury Securities [Member]
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	115,369	40,397
Gross Unrealized Gains	1	0
Gross Unrealized Losses	(708)	(160)
Available-for-sale Securities	114,662	40,237
Non US Government Securities [Member]
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	16,743
Gross Unrealized Gains	0
Gross Unrealized Losses	(180)
Available-for-sale Securities	16,563
Commercial Paper [Member]
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	73,868	111,868
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	0
Available-for-sale Securities	73,868	111,868
Asset-backed Securities [Member]
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	32,400	39,988
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(212)	(62)
Available-for-sale Securities	32,188	39,926
Corporate Debt Securities [Member]
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	94,734	103,779
Gross Unrealized Gains	14	7
Gross Unrealized Losses	(770)	(212)
Available-for-sale Securities	$ 93,978	103,574
Government-Sponsored Agencies [Member]
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost		16,821
Gross Unrealized Gains		0
Gross Unrealized Losses		(56)
Available-for-sale Securities		$ 16,765

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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