Cash, Cash Equivalents and Investment Debt Securities (Cash, Cash Equivalents and Investment Debt Securities) (Details) - USD ($) $ in Thousands	Jun. 30, 2022	Dec. 31, 2021
Cash and cash equivalents:
Cash and Cash Equivalents, Amortized Cost	$ 58,019	$ 84,709
Cash and cash equivalents, Fair Value	58,019	84,709
Investment Debt Securities Abstract
Total investments, Amortized Cost	348,563	335,260
Total cash and cash equivalents and investment debt securities, Amortized Cost	406,582	419,969
Allowance for Credit Losses	0
Total investments, Gross Unrealized Gains	0	16
Total cash and cash equivalents and investment debt securities, Gross Unrealized Gains	0	16
Total investments, Gross Unrealized Losses	(1,806)	(296)
Total cash and cash equivalents and investment debt securities, Gross Unrealized Losses	(1,806)	(296)
Total investments, Fair Value	346,757	334,980
Total cash and cash equivalents and investment debt securities, Fair Value	404,776	419,689
Commercial paper
Investment Debt Securities Abstract
Total investments, Amortized Cost	143,932	84,513
Allowance for Credit Losses	0
Total investments, Gross Unrealized Gains	0
Total investments, Gross Unrealized Losses	(320)	(49)
Total investments, Fair Value	143,612	84,464
Corporate debt securities
Investment Debt Securities Abstract
Total investments, Amortized Cost	180,955	232,721
Allowance for Credit Losses	0
Total investments, Gross Unrealized Gains	0	16
Total investments, Gross Unrealized Losses	(1,319)	(245)
Total investments, Fair Value	179,636	232,492
Municipal bonds
Investment Debt Securities Abstract
Total investments, Amortized Cost		5,028
Total investments, Gross Unrealized Losses		(1)
Total investments, Fair Value		5,027
U.S. government agency bonds
Investment Debt Securities Abstract
Total investments, Amortized Cost	3,500
Total investments, Gross Unrealized Gains	0
Total investments, Gross Unrealized Losses	(58)
Total investments, Fair Value	3,442
U.S Treasury securities
Investment Debt Securities Abstract
Total investments, Amortized Cost	20,176	12,998
Total investments, Gross Unrealized Gains	0
Total investments, Gross Unrealized Losses	(109)	(1)
Total investments, Fair Value	20,067	12,997
Cash and money market funds
Cash and cash equivalents:
Cash and Cash Equivalents, Amortized Cost	58,019	76,709
Cash and cash equivalents, Fair Value	$ 58,019	76,709
Commercial paper
Cash and cash equivalents:
Cash and Cash Equivalents, Amortized Cost		8,000
Cash and cash equivalents, Fair Value		$ 8,000