Significant Accounting Policies (Details) - USD ($) $ in Thousands	Mar. 31, 2022	Dec. 31, 2021	Mar. 31, 2021	Dec. 31, 2020
Significant Accounting Policies
Total investments	$ 15,000	$ 13,000
Temporary cash investments	3,000	2,500
Total investments and temporary cash investments	18,000	15,500
Control Investments [Member]
Significant Accounting Policies
Total investments	15,000	13,000
Level 1 [Member]
Significant Accounting Policies
Total investments	0	0
Temporary cash investments	3,000	2,500
Total investments and temporary cash investments	3,000	2,500
Level 1 [Member] | Control Investments [Member]
Significant Accounting Policies
Total investments	0	0
Level 2 [Member]
Significant Accounting Policies
Total investments	0	0
Temporary cash investments	0	0
Total investments and temporary cash investments	0	0
Level 2 [Member] | Control Investments [Member]
Significant Accounting Policies
Total investments	0	0
Level 3 [Member]
Significant Accounting Policies
Total investments	15,000	13,000	$ 8,500	$ 7,000
Temporary cash investments	0	0
Total investments and temporary cash investments	15,000	13,000
Level 3 [Member] | Control Investments [Member]
Significant Accounting Policies
Total investments	$ 15,000	$ 13,000	$ 8,500	$ 7,000