Fair Value Measurements - Marketable Securities (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	$ 1,610,775	$ 2,114,541
Gross unrealized gains	1,194	9,824
Gross unrealized losses	(5,580)	(339)
Aggregate Fair Value	1,606,389	2,124,026
Short-Term Marketable Securities	540,574	744,290
Long-Term Marketable Securities	1,065,815	1,379,736
Commercial paper
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	25,056	46,931
Gross unrealized gains	0	13
Gross unrealized losses	(24)	(8)
Aggregate Fair Value	25,032	46,936
Short-Term Marketable Securities	25,032	46,936
Long-Term Marketable Securities	0	0
Corporate bonds
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	1,268,991	1,628,462
Gross unrealized gains	1,191	9,482
Gross unrealized losses	(4,275)	(262)
Aggregate Fair Value	1,265,907	1,637,682
Short-Term Marketable Securities	459,012	607,403
Long-Term Marketable Securities	806,895	1,030,279
Municipal securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost		3,495
Gross unrealized gains		0
Gross unrealized losses		(6)
Aggregate Fair Value		3,489
Short-Term Marketable Securities		0
Long-Term Marketable Securities		3,489
U.S. government agency obligations
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	316,728	435,653
Gross unrealized gains	3	329
Gross unrealized losses	(1,281)	(63)
Aggregate Fair Value	315,450	435,919
Short-Term Marketable Securities	56,530	89,951
Long-Term Marketable Securities	$ 258,920	$ 345,968

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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Amount, before tax, of unrealized loss 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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