Consolidated Statements of Operations - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Revenues:
Gross premiums written									$ 590,233	$ 291,253	$ 290,723
Net premiums written									501,244	273,181	271,984
Net premiums earned	$ 123,222	$ 124,707	$ 128,877	$ 127,337	$ 66,930	$ 68,028	$ 66,017	$ 67,544	504,143	268,519	248,722
Net investment income	8,375	8,852	9,141	8,241	6,333	6,527	7,677	8,284	34,609	28,821	37,209
Net realized investment gains (losses):
Other than temporary impairment losses on investments									(7,335)	(501)	(1,239)
Other net realized investment gains									3,961	36,361	28,651
Total net realized investment gains (losses)	3,842	(10,778)	6,532	(2,970)	(4,366)	1,158	39,881	(813)	(3,374)	35,860	27,412
Other income									3,400	555	5,791
Total revenues									538,778	333,755	319,134
Losses and Expenses:
Net losses and loss adjustment expenses	48,498	77,691	79,560	69,619	24,065	36,654	38,270	38,572	275,368	137,561	132,991
Acquisition costs and other underwriting expenses	51,185	50,934	50,926	48,258	28,505	27,458	27,171	26,485	201,303	109,619	105,651
Corporate and other operating expenses									24,448	14,559	11,614
Interest expense									4,913	822	6,169
Income before income taxes	29,463	(9,727)	9,772	3,238	11,294	8,128	44,798	6,974	32,746	71,194	62,709
Income tax expense (benefit)									(8,723)	8,338	1,019
Net income	$ 27,304	$ (3,746)	$ 11,117	$ 6,794	$ 11,064	$ 9,761	$ 33,208	$ 8,823	$ 41,469	$ 62,856	$ 61,690
Net income
Basic									$ 1.71	$ 2.50	$ 2.46
Diluted	$ 1.30	$ (0.15)	$ 0.43	$ 0.26	$ 0.44	$ 0.39	$ 1.31	$ 0.35	$ 1.69	$ 2.48	$ 2.45
Weighted-average number of shares outstanding
Basic									24,253,657	25,131,811	25,072,712
Diluted									24,505,851	25,331,420	25,174,015