Consolidated Statements of Operations - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Revenues:
Gross premiums written									$ 565,845	$ 590,233	$ 291,253
Net premiums written									470,940	501,244	273,181
Net premiums earned	$ 109,472	$ 119,553	$ 117,804	$ 121,636	$ 123,222	$ 124,707	$ 128,877	$ 127,337	468,465	504,143	268,519
Net investment income	8,880	8,795	6,562	9,746	8,375	8,852	9,141	8,241	33,983	34,609	28,821
Net realized investment gains (losses):
Other than temporary impairment losses on investments									(6,733)	(7,335)	(501)
Other net realized investment gains									28,454	3,961	36,361
Total net realized investment gains (losses)	30,778	1,928	(3,492)	(7,493)	3,842	(10,778)	6,532	(2,970)	21,721	(3,374)	35,860
Other income									10,345	3,400	555
Total revenues									534,514	538,778	333,755
Losses and Expenses:
Net losses and loss adjustment expenses	48,946	72,162	78,111	64,784	48,498	77,691	79,560	69,619	264,003	275,368	137,561
Acquisition costs and other underwriting expenses	47,889	48,129	48,542	52,090	51,185	50,934	50,926	48,258	196,650	201,303	109,619
Corporate and other operating expenses									17,338	24,448	14,559
Interest expense									8,905	4,913	822
Income before income taxes	46,535	10,598	(11,468)	1,953	29,463	(9,727)	9,772	3,238	47,618	32,746	71,194
Income tax expense (benefit)									(2,250)	(8,723)	8,338
Net income	$ 38,373	$ 9,535	$ (5,165)	$ 7,125	$ 27,304	$ (3,746)	$ 11,117	$ 6,794	$ 49,868	$ 41,469	$ 62,856
Net income
Basic									$ 2.89	$ 1.71	$ 2.50
Diluted	$ 2.18	$ 0.54	$ (0.30)	$ 0.41	$ 1.30	$ (0.15)	$ 0.43	$ 0.26	$ 2.84	$ 1.69	$ 2.48
Weighted-average number of shares outstanding
Basic									17,246,717	24,253,657	25,131,811
Diluted									17,547,061	24,505,851	25,331,420