Quarterly Financial Information (Unaudited) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2021	Sep. 30, 2021	Jun. 30, 2021	Mar. 31, 2021	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Investment Company, Financial Highlights [Line Items]
Revenues	$ 69,921	$ 61,584	$ 63,558	$ 55,483	$ 64,968	$ 59,825	$ 58,341	$ 55,722	$ 250,546	$ 238,856	$ 250,545
Benefits and expenses	76,734	64,311	57,958	58,231	67,317	67,996	57,903	57,957	257,234	251,173	244,800
Federal income tax expense (benefit)	(44,950)	72	578	825	(3,887)	(256)	1,465	1,349	(43,475)	(1,329)	7,115
Net income (loss)	38,137	(2,799)	5,022	(3,573)	1,538	(7,915)	(1,027)	(3,584)	$ 36,787	$ (10,988)	$ (1,370)
Common Stock [Member]
Investment Company, Financial Highlights [Line Items]
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest	$ 38,137	$ (2,799)	$ 5,022	$ (3,573)	$ 1,538	$ (7,915)	$ (1,027)	$ (3,584)
Common Stock Class A [Member]
Investment Company, Financial Highlights [Line Items]
Earnings Per Share, Basic	$ 0.77	$ (0.06)	$ 0.10	$ (0.07)	$ 0.03	$ (0.16)	$ (0.02)	$ (0.07)	$ 0.74	$ (0.22)	$ (0.03)
Earnings Per Share, Diluted	0.77	(0.06)	0.10	(0.07)	0.03	(0.16)	(0.02)	(0.07)	0.73	(0.22)	(0.03)
Common Stock Class B [Member]
Investment Company, Financial Highlights [Line Items]
Earnings Per Share, Basic	0.36	0	0.05	(0.04)	0.01	(0.07)	(0.01)	(0.04)	0.37	(0.11)	(0.01)
Earnings Per Share, Diluted	$ 0.36	$ 0	$ 0.05	$ (0.04)	$ 0.01	$ (0.07)	$ (0.01)	$ (0.04)	$ 0.36	$ (0.11)	$ (0.01)