Cash and Cash Equivalents, and Investments - Schedule of Available For Sale Securities (Details) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Debt Securities, Available-for-sale [Line Items]
Adjusted Cost	$ 2,513,266
Fair Value	2,513,553
Cash and cash equivalents:
Debt Securities, Available-for-sale [Line Items]
Adjusted Cost	840,056	$ 479,853
Unrealized Gain	0	0
Unrealized Loss	0	0
Fair Value	840,056	479,853
Short-term investments:
Debt Securities, Available-for-sale [Line Items]
Adjusted Cost	1,221,089	664,119
Unrealized Gain	707	1,502
Unrealized Loss	(130)	(54)
Fair Value	1,221,666	665,567
Long-term investments:
Debt Securities, Available-for-sale [Line Items]
Adjusted Cost	485,143	523,270
Unrealized Gain	76	641
Unrealized Loss	(366)	(283)
Fair Value	484,853	523,628
Commercial paper \| Short-term investments:
Debt Securities, Available-for-sale [Line Items]
Adjusted Cost	514,715	204,152
Unrealized Gain	120	24
Unrealized Loss	0	(6)
Fair Value	514,835	204,170
Corporate debt securities \| Short-term investments:
Debt Securities, Available-for-sale [Line Items]
Adjusted Cost	690,873	459,967
Unrealized Gain	566	1,478
Unrealized Loss	(130)	(48)
Fair Value	691,309	461,397
Corporate debt securities \| Long-term investments:
Debt Securities, Available-for-sale [Line Items]
Adjusted Cost	476,143	484,275
Unrealized Gain	75	605
Unrealized Loss	(366)	(283)
Fair Value	475,852	484,597
Agency bonds \| Short-term investments:
Debt Securities, Available-for-sale [Line Items]
Adjusted Cost	15,501
Unrealized Gain	21
Unrealized Loss	0
Fair Value	15,522
Agency bonds \| Long-term investments:
Debt Securities, Available-for-sale [Line Items]
Adjusted Cost	9,000	38,995
Unrealized Gain	1	36
Unrealized Loss	0	0
Fair Value	9,001	39,031
Cash \| Cash and cash equivalents:
Debt Securities, Available-for-sale [Line Items]
Adjusted Cost	33,022	15,054
Unrealized Gain	0	0
Unrealized Loss	0	0
Fair Value	33,022	15,054
Money market funds \| Cash and cash equivalents:
Debt Securities, Available-for-sale [Line Items]
Adjusted Cost	807,034	464,799
Unrealized Gain	0	0
Unrealized Loss	0	0
Fair Value	$ 807,034	$ 464,799

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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