Supplementary Balance Sheet Information - Short-term Investments (Details) - USD ($)	12 Months Ended
Dec. 31, 2022	Dec. 31, 2021
Maturity less than 1 year:
Amortized Cost	$ 84,299,000	$ 95,643,000
Gross Unrealized Gains	19,000	6,000
Gross Unrealized Losses	(394,000)	(65,000)
Fair Market Value	83,924,000	95,584,000
Maturity 1 to 2 years:
Amortized Cost	5,016,000	33,377,000
Gross Unrealized Gains	1,000	1,000
Gross Unrealized Losses	(21,000)	(84,000)
Fair Market Value	4,996,000	33,294,000
Amortized Cost	89,315,000	129,020,000
Gross Unrealized Gains	20,000	7,000
Gross Unrealized Losses	(415,000)	(149,000)
Fair Market Value	88,920,000	128,878,000
Realized loss	200,000
Certificate of deposit
Maturity less than 1 year:
Amortized Cost	16,101,000	1,260,000
Gross Unrealized Gains	3,000	0
Gross Unrealized Losses	(81,000)	0
Fair Market Value	16,023,000	1,260,000
Corporate debt securities
Maturity less than 1 year:
Amortized Cost	44,806,000	58,822,000
Gross Unrealized Gains	8,000	2,000
Gross Unrealized Losses	(275,000)	(38,000)
Fair Market Value	44,539,000	58,786,000
Maturity 1 to 2 years:
Amortized Cost	5,016,000	29,676,000
Gross Unrealized Gains	1,000	1,000
Gross Unrealized Losses	(21,000)	(73,000)
Fair Market Value	4,996,000	29,604,000
Commercial paper
Maturity less than 1 year:
Amortized Cost	13,203,000	14,453,000
Gross Unrealized Gains	4,000	4,000
Gross Unrealized Losses	(20,000)	(3,000)
Fair Market Value	13,187,000	14,454,000
U.S. government agencies
Maturity less than 1 year:
Amortized Cost	2,284,000
Gross Unrealized Gains	4,000
Gross Unrealized Losses	0
Fair Market Value	2,288,000
Non U.S. government
Maturity less than 1 year:
Amortized Cost		728,000
Gross Unrealized Gains		0
Gross Unrealized Losses		0
Fair Market Value		728,000
U.S. treasury securities
Maturity less than 1 year:
Amortized Cost	7,905,000	20,380,000
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(18,000)	(24,000)
Fair Market Value	$ 7,887,000	20,356,000
Maturity 1 to 2 years:
Amortized Cost		3,701,000
Gross Unrealized Gains		0
Gross Unrealized Losses		(11,000)
Fair Market Value		$ 3,690,000

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