Financial Instruments and Fair Value Measurements - Unrealized Loss Position (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Debt Securities, Available-for-sale [Line Items]
Gross Unrealized Losses, Less than 12 months	$ (152)	$ (40)
Estimated Fair Value, Less than 12 months	588,540	85,161
Gross Unrealized Losses, 12 months or more	0	0
Estimated Fair Value, 12 months or more	0	0
Gross Unrealized Losses, Total	(152)	(40)
Estimated Fair Value, Total	588,540	85,161
Certificates of deposit
Debt Securities, Available-for-sale [Line Items]
Gross Unrealized Losses, Less than 12 months	(4)	(6)
Estimated Fair Value, Less than 12 months	81,524	12,822
Gross Unrealized Losses, 12 months or more	0	0
Estimated Fair Value, 12 months or more	0	0
Gross Unrealized Losses, Total	(4)	(6)
Estimated Fair Value, Total	81,524	12,822
U.S. treasury securities
Debt Securities, Available-for-sale [Line Items]
Gross Unrealized Losses, Less than 12 months		(2)
Estimated Fair Value, Less than 12 months		9,979
Gross Unrealized Losses, 12 months or more		0
Estimated Fair Value, 12 months or more		0
Gross Unrealized Losses, Total		(2)
Estimated Fair Value, Total		9,979
Debt securities of U.S. government agencies and corporate entities
Debt Securities, Available-for-sale [Line Items]
Gross Unrealized Losses, Less than 12 months	(148)	(32)
Estimated Fair Value, Less than 12 months	507,016	62,360
Gross Unrealized Losses, 12 months or more	0	0
Estimated Fair Value, 12 months or more	0	0
Gross Unrealized Losses, Total	(148)	(32)
Estimated Fair Value, Total	$ 507,016	$ 62,360

Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), in continuous unrealized loss position for more than 12 months, without allowance for credit loss. Includes beneficial interest in securitized financial asset.

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