Investments - Amortized Cost (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Debt Securities, Available-for-sale [Line Items]
Cost	$ 419,783	$ 409,996
Gross Unrealized Gains	14	47
Gross Unrealized Losses	(922)	(12)
Fair Value	418,875	410,031
Included in cash and cash equivalents
Debt Securities, Available-for-sale [Line Items]
Cost	950	133,319
Gross Unrealized Gains	0	4
Gross Unrealized Losses	0	(2)
Fair Value	950	133,321
Included in marketable securities
Debt Securities, Available-for-sale [Line Items]
Cost	418,833	276,677
Gross Unrealized Gains	14	43
Gross Unrealized Losses	(922)	(10)
Fair Value	417,925	276,710
U.S. treasury securities
Debt Securities, Available-for-sale [Line Items]
Cost	161,938	155,339
Gross Unrealized Gains	1	14
Gross Unrealized Losses	(474)	(6)
Fair Value	161,465	155,347
U.S. agency and government sponsored securities
Debt Securities, Available-for-sale [Line Items]
Cost	4,995	19,996
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(25)	0
Fair Value	4,970	19,996
Commercial paper
Debt Securities, Available-for-sale [Line Items]
Cost	40,788	182,218
Gross Unrealized Gains	0	6
Gross Unrealized Losses	(4)	(4)
Fair Value	40,784	182,220
Corporate bonds
Debt Securities, Available-for-sale [Line Items]
Cost	165,522	45,431
Gross Unrealized Gains	13	21
Gross Unrealized Losses	(345)	(2)
Fair Value	165,190	45,450
Asset-backed securities
Debt Securities, Available-for-sale [Line Items]
Cost	46,540	7,012
Gross Unrealized Gains	0	6
Gross Unrealized Losses	(74)	0
Fair Value	$ 46,466	$ 7,018