Financial Instruments (Details) $ in Thousands	Jun. 30, 2023 USD ($) position	Dec. 31, 2022 USD ($)
Debt Securities, Available-for-sale, Fair Value to Amortized Cost [Abstract]
Amortized Cost	$ 708,596	$ 857,357
Gross Unrealized Gain		1
Gross Unrealized Loss	(8,869)	(16,103)
Estimated Fair Value	$ 699,727	841,255
Number of investments, unrealized loss position | position	47
Fair value	$ 351,820
Unrealized loss	(8,869)
Gross unrealized loss	8,869	16,103
Amortized Cost
Less than or equal to one year	296,067
Greater than one year but less than five years	67,630
Total	363,697
Fair Value
Less than or equal to one year	291,495
Greater than or equal to one year but less than five years	63,333
Total	354,828
Money market deposits
Debt Securities, Available-for-sale, Fair Value to Amortized Cost [Abstract]
Amortized Cost	216,337	283,358
Estimated Fair Value	216,337	283,358
Liquid demand deposits
Debt Securities, Available-for-sale, Fair Value to Amortized Cost [Abstract]
Amortized Cost	128,562	125,596
Estimated Fair Value	128,562	125,596
U.S. Treasury securities
Debt Securities, Available-for-sale, Fair Value to Amortized Cost [Abstract]
Amortized Cost	302,590	358,385
Gross Unrealized Loss	(6,100)	(12,328)
Estimated Fair Value	296,490	346,057
Fair value	296,490
Unrealized loss	(6,100)
Gross unrealized loss	6,100	12,328
Corporate bonds and notes
Debt Securities, Available-for-sale, Fair Value to Amortized Cost [Abstract]
Amortized Cost	9,002	24,045
Gross Unrealized Loss	(101)	(516)
Estimated Fair Value	8,901	23,529
Fair value	8,901
Unrealized loss	(101)
Gross unrealized loss	101	516
Municipal securities
Debt Securities, Available-for-sale, Fair Value to Amortized Cost [Abstract]
Amortized Cost	52,105	65,973
Gross Unrealized Gain		1
Gross Unrealized Loss	(2,668)	(3,259)
Estimated Fair Value	49,437	62,715
Fair value	46,429
Unrealized loss	(2,668)
Gross unrealized loss	2,668	3,259
Available-for-sale securities
Debt Securities, Available-for-sale, Fair Value to Amortized Cost [Abstract]
Fair value	0
Cash equivalents
Debt Securities, Available-for-sale, Fair Value to Amortized Cost [Abstract]
Estimated Fair Value	344,899	408,954
Short-term investments
Debt Securities, Available-for-sale, Fair Value to Amortized Cost [Abstract]
Estimated Fair Value	$ 354,828	$ 432,301