Financial Instruments (Details) $ in Thousands	3 Months Ended
Mar. 31, 2022 USD ($) position	Dec. 31, 2021 USD ($)
Debt Securities, Available-for-sale, Fair Value to Amortized Cost [Abstract]
Amortized Cost	$ 663,805	$ 842,224
Gross Unrealized Gain	3	1,342
Gross Unrealized Loss	(13,774)	(3,629)
Estimated Fair Value	650,034	839,937
Proceeds from investments sold	166,900
Realized gain	100
Other than temporary impairment	$ 0
Number of investments, unrealized loss position \| position	74
Amortized Cost
Less than or equal to one year	$ 161,807
Greater than one year but less than five years	445,624
Total	607,431
Fair Value
Less than or equal to one year	160,782
Greater than or equal to one year but less than five years	432,878
Total	593,660
Available-for-sale securities
Debt Securities, Available-for-sale, Fair Value to Amortized Cost [Abstract]
Gross Unrealized Loss	(13,800)
Unrealized loss position	587,100
Money market deposits
Debt Securities, Available-for-sale, Fair Value to Amortized Cost [Abstract]
Amortized Cost	56,374	10,041
Estimated Fair Value	56,374	10,041
U.S. Treasury securities
Debt Securities, Available-for-sale, Fair Value to Amortized Cost [Abstract]
Amortized Cost	485,265	689,640
Gross Unrealized Gain		1,081
Gross Unrealized Loss	(10,416)	(2,624)
Estimated Fair Value	474,849	688,097
Corporate bonds and notes
Debt Securities, Available-for-sale, Fair Value to Amortized Cost [Abstract]
Amortized Cost	46,499	52,729
Gross Unrealized Loss	(833)	(392)
Estimated Fair Value	45,666	52,337
Municipal securities
Debt Securities, Available-for-sale, Fair Value to Amortized Cost [Abstract]
Amortized Cost	75,667	89,814
Gross Unrealized Gain	3	261
Gross Unrealized Loss	(2,525)	(613)
Estimated Fair Value	73,145	89,462
Cash equivalents
Debt Securities, Available-for-sale, Fair Value to Amortized Cost [Abstract]
Estimated Fair Value	56,374	10,041
Short-term investments
Debt Securities, Available-for-sale, Fair Value to Amortized Cost [Abstract]
Estimated Fair Value	$ 593,660	$ 829,896

Amount of cash, cash equivalents, restricted cash and investment in marketable securities.

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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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