Fair Value Measurements - Financial Instruments (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020	Apr. 24, 2020
Assets:
Debt securities, Estimated Fair Value	$ 149,783	$ 151,999
Equity Securities	9,437	17,336
Short-term investments	23,013	13,317
Total marketable investments measured at fair value	182,233	182,652
Total assets measured at fair value	182,727	183,207
Liabilities:
Total Liabilities measured at fair value	35,822	40,036
Debt	33,564	40,997
Line of credit
Liabilities:
Debt	0	5,000
Paycheck Protection Program
Liabilities:
Debt	0	2,745	$ 2,700
U.S. Government
Assets:
Debt securities, Estimated Fair Value	20,720	30,967
State and local government
Assets:
Debt securities, Estimated Fair Value	30,429	33,265
Corporate debt
Assets:
Debt securities, Estimated Fair Value	30,346	19,303
Asset-backed securities
Assets:
Debt securities, Estimated Fair Value	28,438	20,963
Mortgage-backed securities
Assets:
Debt securities, Estimated Fair Value	32,521	38,854
Commercial mortgage-backed securities
Assets:
Debt securities, Estimated Fair Value	1,690	2,126
Collateralized mortgage obligations
Assets:
Debt securities, Estimated Fair Value	5,639	6,521
Senior Unsecured Notes
Liabilities:
Debt	24,118	20,675
Subordinated notes
Liabilities:
Debt	11,704	11,616
Partnership interest
Assets:
Investments measured at NAV	494	555
Level 1
Assets:
Debt securities, Estimated Fair Value	0	0
Equity Securities	9,154	17,053
Short-term investments	23,013	13,317
Total marketable investments measured at fair value	32,167	30,370
Liabilities:
Total Liabilities measured at fair value	0	0
Level 1 | U.S. Government
Assets:
Debt securities, Estimated Fair Value	0	0
Level 1 | State and local government
Assets:
Debt securities, Estimated Fair Value	0	0
Level 1 | Corporate debt
Assets:
Debt securities, Estimated Fair Value	0	0
Level 1 | Asset-backed securities
Assets:
Debt securities, Estimated Fair Value	0	0
Level 1 | Mortgage-backed securities
Assets:
Debt securities, Estimated Fair Value	0	0
Level 1 | Commercial mortgage-backed securities
Assets:
Debt securities, Estimated Fair Value	0	0
Level 1 | Collateralized mortgage obligations
Assets:
Debt securities, Estimated Fair Value	0	0
Level 1 | Senior Unsecured Notes
Liabilities:
Debt	0	0
Level 1 | Subordinated notes
Liabilities:
Debt	0	0
Level 2
Assets:
Debt securities, Estimated Fair Value	149,783	151,999
Equity Securities	283	283
Short-term investments	0
Total marketable investments measured at fair value	150,066	152,282
Liabilities:
Total Liabilities measured at fair value	24,118	28,420
Level 2 | Line of credit
Liabilities:
Debt		5,000
Level 2 | Paycheck Protection Program
Liabilities:
Debt		2,745
Level 2 | U.S. Government
Assets:
Debt securities, Estimated Fair Value	20,720	30,967
Level 2 | State and local government
Assets:
Debt securities, Estimated Fair Value	30,429	33,265
Level 2 | Corporate debt
Assets:
Debt securities, Estimated Fair Value	30,346	19,303
Level 2 | Asset-backed securities
Assets:
Debt securities, Estimated Fair Value	28,438	20,963
Level 2 | Mortgage-backed securities
Assets:
Debt securities, Estimated Fair Value	32,521	38,854
Level 2 | Commercial mortgage-backed securities
Assets:
Debt securities, Estimated Fair Value	1,690	2,126
Level 2 | Collateralized mortgage obligations
Assets:
Debt securities, Estimated Fair Value	5,639	6,521
Level 2 | Senior Unsecured Notes
Liabilities:
Debt	24,118	20,675
Level 2 | Subordinated notes
Liabilities:
Debt	0	0
Level 3
Assets:
Debt securities, Estimated Fair Value	0	0
Equity Securities	0	0
Short-term investments	0	0
Total marketable investments measured at fair value	0	0
Liabilities:
Total Liabilities measured at fair value	11,704	11,616
Level 3 | U.S. Government
Assets:
Debt securities, Estimated Fair Value	0	0
Level 3 | State and local government
Assets:
Debt securities, Estimated Fair Value	0	0
Level 3 | Corporate debt
Assets:
Debt securities, Estimated Fair Value	0	0
Level 3 | Asset-backed securities
Assets:
Debt securities, Estimated Fair Value	0	0
Level 3 | Mortgage-backed securities
Assets:
Debt securities, Estimated Fair Value	0	0
Level 3 | Commercial mortgage-backed securities
Assets:
Debt securities, Estimated Fair Value	0	0
Level 3 | Collateralized mortgage obligations
Assets:
Debt securities, Estimated Fair Value	0	0
Level 3 | Senior Unsecured Notes
Liabilities:
Debt	0	0
Level 3 | Subordinated notes
Liabilities:
Debt	$ 11,704	$ 11,616