Cash, Cash Equivalents, Restricted Cash and Marketable Securities - Summary of Cash, Cash Equivalents and Marketable Securities (Detail) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Cash Cash Equivalents And Marketable Securities [Line Items]
Amortized Cost	$ 414,113	$ 165,005
Unrealized Gains	42	48
Unrealized Losses		(17)
Estimated Fair Value	414,155	165,036
Cash and Cash Equivalents
Cash Cash Equivalents And Marketable Securities [Line Items]
Amortized Cost	246,351	32,073
Estimated Fair Value	246,351	32,073
Marketable Securities Available-for-Sale
Cash Cash Equivalents And Marketable Securities [Line Items]
Amortized Cost	167,762	132,932
Unrealized Gains	42	48
Unrealized Losses		(17)
Estimated Fair Value	167,804	132,963
Cash | Cash and Cash Equivalents
Cash Cash Equivalents And Marketable Securities [Line Items]
Amortized Cost	4,900	7,945
Estimated Fair Value	4,900	7,945
Money Market Funds | Cash and Cash Equivalents
Cash Cash Equivalents And Marketable Securities [Line Items]
Amortized Cost	241,451	23,128
Estimated Fair Value	241,451	23,128
U.S. Treasuries | Marketable Securities Available-for-Sale
Cash Cash Equivalents And Marketable Securities [Line Items]
Amortized Cost	12,279	32,548
Unrealized Gains	2	31
Estimated Fair Value	12,281	32,579
U.S. Government Agency Securities | Marketable Securities Available-for-Sale
Cash Cash Equivalents And Marketable Securities [Line Items]
Amortized Cost	36,338	40,313
Unrealized Gains	5	14
Unrealized Losses		(6)
Estimated Fair Value	36,343	40,321
Corporate Debt Securities | Cash and Cash Equivalents
Cash Cash Equivalents And Marketable Securities [Line Items]
Amortized Cost		1,000
Estimated Fair Value		1,000
Corporate Debt Securities | Marketable Securities Available-for-Sale
Cash Cash Equivalents And Marketable Securities [Line Items]
Amortized Cost	119,145	60,071
Unrealized Gains	35	3
Unrealized Losses		(11)
Estimated Fair Value	$ 119,180	$ 60,063