Consolidated Statements of Stockholder's Equity Statement - USD ($) $ in Thousands	Total	Accumulated deficit [Member]	Accumulated other comprehensive income [Member]	Treasury stock [Member]	Common Stock Class A [Member] Common stock [Member]	Common Stock Class B [Member] Common stock [Member]
Balance at Dec. 31, 2019	$ 259,836	$ (70,969)	$ 77,117	$ (11,011)	$ 261,515	$ 3,184
Net income (loss)	(3,584)	(3,584)	0	0	0	0
Unrealized investment gains (losses), net	(40,070)	0	(40,070)	0	0	0
Comprehensive income (loss)	(43,654)	(3,584)	(40,070)	0	0	0
Stock-based compensation	(53)	0	0	0	(53)	0
Balance at Mar. 31, 2020	215,734	(74,948)	37,047	(11,011)	261,462	3,184
Balance at Dec. 31, 2020	300,945	(82,352)	128,255	(11,011)	262,869	3,184
Net income (loss)	(3,573)	(3,573)	0	0	0	0
Unrealized investment gains (losses), net	(56,518)	0	(56,518)	0	0	0
Comprehensive income (loss)	(60,091)	(3,573)	(56,518)	0	0	0
Stock-based compensation	(14)	0	0	0	(14)	0
Balance at Mar. 31, 2021	$ 240,840	$ (85,925)	$ 71,737	$ (11,011)	$ 262,855	$ 3,184