Fair Value Measurements - Marketable Securities (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2022	Dec. 31, 2021
Marketable Securities [Line Items]
Amortized Cost	$ 917,888	$ 1,610,775
Gross Unrealized Gains	0	1,194
Gross Unrealized Losses	(24,759)	(5,580)
Aggregate Fair Value	893,129	1,606,389
Short-Term Marketable Securities	128,287	540,574
Long-Term Marketable Securities	764,842	1,065,815
Commercial paper
Marketable Securities [Line Items]
Amortized Cost		25,056
Gross Unrealized Gains		0
Gross Unrealized Losses		(24)
Aggregate Fair Value		25,032
Short-Term Marketable Securities		25,032
Long-Term Marketable Securities		0
Corporate bonds
Marketable Securities [Line Items]
Amortized Cost	645,755	1,268,991
Gross Unrealized Gains	0	1,191
Gross Unrealized Losses	(17,750)	(4,275)
Aggregate Fair Value	628,005	1,265,907
Short-Term Marketable Securities	108,981	459,012
Long-Term Marketable Securities	519,024	806,895
Available-for-sale marketable securities, continuous unrealized loss position for more than 12 months	43,800
Unrealized loss related to corporate bonds	1,100
U.S. government agency obligations
Marketable Securities [Line Items]
Amortized Cost	272,133	316,728
Gross Unrealized Gains	0	3
Gross Unrealized Losses	(7,009)	(1,281)
Aggregate Fair Value	265,124	315,450
Short-Term Marketable Securities	19,306	56,530
Long-Term Marketable Securities	$ 245,818	$ 258,920