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, 2017	$ 223,513	$ (54,375)	$ 26,332	$ (11,011)	$ 259,383	$ 3,184
Net income (loss)	37	37	0	0	0	0
Unrealized investment gains (losses), net	(14,104)	0	(14,104)	0	0	0
Comprehensive income (loss)	(14,067)	37	(14,104)	0	0	0
Balance at Mar. 31, 2018	209,446	(58,500)	16,390	(11,011)	259,383	3,184
Balance at Dec. 31, 2017	223,513	(54,375)	26,332	(11,011)	259,383	3,184
Net income (loss)	(2,521)	(2,521)
Comprehensive income (loss)	(26,296)
Balance at Jun. 30, 2018	197,430	(61,058)	6,719	(11,011)	259,596	3,184
Balance at Mar. 31, 2018	209,446	(58,500)	16,390	(11,011)	259,383	3,184
Net income (loss)	(2,558)	(2,558)	0	0	0	0
Unrealized investment gains (losses), net	(9,671)	0	(9,671)	0	0	0
Comprehensive income (loss)	(12,229)	(2,558)	(9,671)	0	0	0
Stock-based compensation	213	0	0	0	213	0
Balance at Jun. 30, 2018	197,430	(61,058)	6,719	(11,011)	259,596	3,184
Balance at Dec. 31, 2018	187,733	(69,599)	5,366	(11,011)	259,793	3,184
Net income (loss)	(3,802)	(3,802)	0	0	0	0
Unrealized investment gains (losses), net	26,880	0	26,880	0	0	0
Comprehensive income (loss)	23,078	(3,802)	26,880	0	0	0
Stock-based compensation	1,083	0	0	0	1,083	0
Balance at Mar. 31, 2019	211,894	(73,401)	32,246	(11,011)	260,876	3,184
Balance at Dec. 31, 2018	187,733	(69,599)	5,366	(11,011)	259,793	3,184
Net income (loss)	(8,367)	(8,367)
Comprehensive income (loss)	47,489
Balance at Jun. 30, 2019	236,432	(77,966)	61,222	(11,011)	261,003	3,184
Balance at Mar. 31, 2019	211,894	(73,401)	32,246	(11,011)	260,876	3,184
Net income (loss)	(4,565)	(4,565)	0	0	0	0
Unrealized investment gains (losses), net	28,976	0	28,976	0	0	0
Comprehensive income (loss)	24,411	(4,565)	28,976	0	0	0
Stock-based compensation	127	0	0	0	127	0
Balance at Jun. 30, 2019	$ 236,432	$ (77,966)	$ 61,222	$ (11,011)	$ 261,003	$ 3,184