Marketable Securities - Summary of Cash Equivalents and Marketable Securities Recorded at Fair Value (Detail) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Marketable Securities [Line Items]
Cash equivalents, amortized cost	$ 517,383	$ 773,560
Cash equivalents, gross unrealized gains		1
Cash equivalents, gross unrealized losses	(1)	(24)
Cash equivalents, fair value	517,382	773,537
Marketable securities, amortized cost	1,461,200	521,820
Marketable securities, gross unrealized gains	16	51
Marketable securities, gross unrealized losses	(5,118)	(158)
Marketable securities, fair value	1,456,098	521,713
Cash equivalents and marketable securities, amortized cost	1,978,583	1,295,380
Cash equivalents and marketable securities, gross unrealized gains	16	52
Cash equivalents and marketable securities, gross unrealized losses	(5,119)	(182)
Cash equivalents and marketable securities, fair value	1,973,480	1,295,250
Money Market Funds [Member]
Marketable Securities [Line Items]
Cash equivalents, amortized cost	507,386	742,958
Cash equivalents, fair value	507,386	742,958
Certificates of Deposit [Member]
Marketable Securities [Line Items]
Cash equivalents, amortized cost		12,527
Cash equivalents, fair value		12,527
Marketable securities, amortized cost	45,164	25,162
Marketable securities, fair value	45,164	25,162
Commercial Paper [Member]
Marketable Securities [Line Items]
Cash equivalents, amortized cost	9,997	15,549
Cash equivalents, gross unrealized losses	(1)
Cash equivalents, fair value	9,996	15,549
Marketable securities, amortized cost	212,805	90,375
Marketable securities, gross unrealized losses	(86)
Marketable securities, fair value	212,719	90,375
US Treasury Securities [Member]
Marketable Securities [Line Items]
Marketable securities, amortized cost	16,238	47,976
Marketable securities, gross unrealized gains	6	3
Marketable securities, gross unrealized losses	(52)
Marketable securities, fair value	16,192	47,979
Corporate Debt Securities [Member]
Marketable Securities [Line Items]
Cash equivalents, amortized cost		2,526
Cash equivalents, gross unrealized gains		1
Cash equivalents, gross unrealized losses		(24)
Cash equivalents, fair value		2,503
Marketable securities, amortized cost	1,173,659	324,569
Marketable securities, gross unrealized gains	10	43
Marketable securities, gross unrealized losses	(4,903)	(156)
Marketable securities, fair value	1,168,766	324,456
Government-sponsored Enterprise Securities [Member]
Marketable Securities [Line Items]
Marketable securities, amortized cost	13,334	33,738
Marketable securities, gross unrealized gains		5
Marketable securities, gross unrealized losses	(77)	(2)
Marketable securities, fair value	$ 13,257	$ 33,741