Fair Value Measurements - Financial Instruments (Details) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020	Apr. 24, 2020
Assets:
Total debt securities	$ 149,188	$ 151,999
Equity Securities	19,314	17,336
Short-term investments	11,435	13,317
Total marketable investments measured at fair value	179,937	182,652
Total assets measured at fair value	180,617	183,207
Liabilities:
Debt	37,153	40,997
Total Liabilities measured at fair value	39,632	40,036
Paycheck Protection Program
Liabilities:
Debt	2,745	2,745	$ 2,700
Line of credit
Liabilities:
Debt	1,000	5,000
U.S. Government
Assets:
Total debt securities	22,057	30,967
State and local government
Assets:
Total debt securities	32,171	33,265
Corporate debt
Assets:
Total debt securities	19,943	19,303
Asset-backed securities
Assets:
Total debt securities	31,627	20,963
Mortgage-backed securities
Assets:
Total debt securities	34,457	38,854
Commercial mortgage-backed securities
Assets:
Total debt securities	1,906	2,126
Collateralized mortgage obligations
Assets:
Total debt securities	7,027	6,521
Senior Unsecured Notes
Liabilities:
Debt	24,283	20,675
Subordinated notes
Liabilities:
Debt	11,604	11,616
Level 1
Assets:
Total debt securities	0	0
Equity Securities	19,031	17,053
Short-term investments	11,435	13,317
Total marketable investments measured at fair value	30,466	30,370
Liabilities:
Total Liabilities measured at fair value	0	0
Level 1 | U.S. Government
Assets:
Total debt securities	0	0
Level 1 | State and local government
Assets:
Total debt securities	0	0
Level 1 | Corporate debt
Assets:
Total debt securities	0	0
Level 1 | Asset-backed securities
Assets:
Total debt securities	0	0
Level 1 | Mortgage-backed securities
Assets:
Total debt securities	0	0
Level 1 | Commercial mortgage-backed securities
Assets:
Total debt securities	0	0
Level 1 | Collateralized mortgage obligations
Assets:
Total debt securities	0	0
Level 1 | Senior Unsecured Notes
Liabilities:
Debt	0	0
Level 1 | Subordinated notes
Liabilities:
Debt	0	0
Level 2
Assets:
Total debt securities	149,188	151,999
Equity Securities	283	283
Short-term investments	0	0
Total marketable investments measured at fair value	149,471	152,282
Liabilities:
Total Liabilities measured at fair value	28,028	28,420
Level 2 | Paycheck Protection Program
Liabilities:
Debt	2,745	2,745
Level 2 | Line of credit
Liabilities:
Debt	1,000	5,000
Level 2 | U.S. Government
Assets:
Total debt securities	22,057	30,967
Level 2 | State and local government
Assets:
Total debt securities	32,171	33,265
Level 2 | Corporate debt
Assets:
Total debt securities	19,943	19,303
Level 2 | Asset-backed securities
Assets:
Total debt securities	31,627	20,963
Level 2 | Mortgage-backed securities
Assets:
Total debt securities	34,457	38,854
Level 2 | Commercial mortgage-backed securities
Assets:
Total debt securities	1,906	2,126
Level 2 | Collateralized mortgage obligations
Assets:
Total debt securities	7,027	6,521
Level 2 | Senior Unsecured Notes
Liabilities:
Debt	24,283	20,675
Level 2 | Subordinated notes
Liabilities:
Debt		0
Level 3
Assets:
Total debt securities	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	11,604	11,616
Level 3 | U.S. Government
Assets:
Total debt securities	0	0
Level 3 | State and local government
Assets:
Total debt securities	0	0
Level 3 | Corporate debt
Assets:
Total debt securities	0	0
Level 3 | Asset-backed securities
Assets:
Total debt securities	0	0
Level 3 | Mortgage-backed securities
Assets:
Total debt securities	0	0
Level 3 | Commercial mortgage-backed securities
Assets:
Total debt securities	0	0
Level 3 | Collateralized mortgage obligations
Assets:
Total debt securities	0	0
Level 3 | Senior Unsecured Notes
Liabilities:
Debt	0	0
Level 3 | Subordinated notes
Liabilities:
Debt	11,604	11,616
Partnership interest
Assets:
Investments measured at NAV	$ 680	$ 555