Quarterly Financial Results (Details) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Revenues
Gross premiums written	$ 253,802	$ 126,403	$ 145,508	$ 87,587	$ 162,277	$ 45,425	$ 98,215	$ 96,020	$ 613,300	$ 401,937	$ 190,374
Gross premiums ceded	0	(150)	0	0	0	0	0	(9,975)	(150)	(9,975)	0
Net premiums written	253,802	126,253	145,508	87,587	162,277	45,425	98,215	86,045	613,150	391,962	190,374
Change in net unearned premium reserves	(70,230)	(17,305)	(66,758)	(14,325)	(103,767)	20,904	(35,928)	(52,504)	(168,618)	(171,295)	(93,893)
Net premiums earned	183,572	108,948	78,750	73,262	58,510	66,329	62,287	33,541	444,532	220,667	96,481
Net investment income	(6,490)	1,552	40,485	50,035	89,321	54,617	32,826	81,361	85,582	258,125	136,868
Total revenues	177,082	110,500	119,235	123,297	147,831	120,946	95,113	114,902	530,114	478,792	233,349
Expenses
Loss and loss adjustment expenses incurred, net	132,364	60,115	44,409	46,259	36,133	39,349	45,692	18,638	283,147	139,812	80,306
Acquisition costs, net	43,875	38,317	29,583	25,431	18,833	21,117	14,921	13,073	137,206	67,944	24,604
General and administrative expenses	10,310	10,124	9,549	10,025	8,965	9,846	7,217	7,008	40,008	33,036	27,376
Other expenses	2,606	2,982	1,020	787	2,247	1,246	759	670	7,395	4,922	446
Total expenses	189,155	111,538	84,561	82,502	66,178	71,558	68,589	39,389	467,756	245,714	132,732
Income before income tax expense	(12,073)	(1,038)	34,674	40,795					62,358	233,078	100,617
Income tax expense	(1,731)	(1,542)	(2,375)	0					(5,648)	0	0
Income including non-controlling interests	(13,804)	(2,580)	32,299	40,795	81,653	49,388	26,524	75,513	56,710	233,078	100,617
Income attributable to non-controlling interests	(875)	(3,417)	(1,007)	(1,016)	(1,565)	(2,818)	(301)	(1,083)	(6,315)	(5,767)	(1,216)
Net income	$ (14,679)	$ (5,997)	$ 31,292	$ 39,779	$ 80,088	$ 46,570	$ 26,223	$ 74,430	$ 50,395	$ 227,311	$ 99,401
Earnings per share
Basic (in dollars per share)	$ (0.14)	$ (0.06)	$ 0.30	$ 0.38	$ 0.77	$ 0.52	$ 0.33	$ 0.94	$ 0.48	$ 2.58	$ 1.26
Diluted (in dollars per share)	$ (0.14)	$ (0.06)	$ 0.29	$ 0.37	$ 0.75	$ 0.51	$ 0.33	$ 0.93	$ 0.47	$ 2.54	$ 1.26
Weighted average number of common shares used in the determination of earnings per share
Basic (in shares)	103,324,616	103,295,920	103,264,616	103,264,616	103,264,616	89,620,394	78,432,132	78,432,132	103,287,693	87,505,540	78,432,132
Diluted (in shares)	103,324,616	103,295,920	106,433,881	103,413,580	106,390,339	90,915,805	79,254,268	79,083,675	106,391,059	88,970,531	78,598,236