Marketable Securities - Gross Unrealized Losses in Fixed Maturity Securities (Details) - USD ($) $ in Thousands	Mar. 31, 2022	Dec. 31, 2021
Fair Value
Less Than 12 Months	$ 51,415	$ 88,999
12 Months or More	459	716
Total	51,874	89,715
Unrealized Losses
Less Than 12 Months	(148)	(94)
12 Months or More	(27)	(6)
Total	(175)	(100)
Corporate bonds
Fair Value
Less Than 12 Months	29,890	56,902
12 Months or More	209	376
Total	30,099	57,278
Unrealized Losses
Less Than 12 Months	(98)	(69)
12 Months or More	(16)	(3)
Total	(114)	(72)
Municipal bonds
Fair Value
Less Than 12 Months	19,289	19,945
12 Months or More	133	340
Total	19,422	20,285
Unrealized Losses
Less Than 12 Months	(32)	(7)
12 Months or More	(8)	(3)
Total	(40)	(10)
Foreign governments
Fair Value
Less Than 12 Months	2,236	12,152
12 Months or More	117	0
Total	2,353	12,152
Unrealized Losses
Less Than 12 Months	(18)	(18)
12 Months or More	(3)	0
Total	$ (21)	$ (18)