Reinsurance (Details) - USD ($)		3 Months Ended		9 Months Ended
	Jul. 01, 2015	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015	Dec. 31, 2015	Dec. 31, 2014
Reinsurance Disclosures [Abstract]
Premiums earned - Direct		$ 270,718,000	$ 252,951,000	$ 789,671,000	$ 738,870,000
Premiums earned - Assumed		152,000	285,000	542,000	931,000
Premiums earned - Ceded		(33,494,000)	(14,002,000)	(100,040,000)	(69,771,000)
Net premiums earned		237,376,000	239,234,000	690,173,000	670,030,000
Losses incurred - Direct		69,579,000	81,699,000	216,874,000	265,445,000
Losses incurred - Assumed		241,000	425,000	681,000	1,191,000
Losses incurred - Ceded		(8,923,000)	(5,666,000)	(25,056,000)	(18,155,000)
Net losses incurred		60,897,000	76,458,000	192,499,000	248,481,000
Premiums Written and Earned [Abstract]
Ceded losses incurred		8,923,000	5,666,000	25,056,000	18,155,000
Reinsurance recoverable on loss reserves		46,863,000	38,748,000	$ 46,863,000	38,748,000	$ 44,487,000	$ 57,841,000
Period of existing captive reinsurance agreement				10 years
Reinsurance recoverable on loss reserves related to captive agreements		20,000,000		$ 20,000,000		34,000,000
Fair value of trust fund assets under captive agreements		94,000,000		94,000,000		137,000,000
Quota Share Reinsurance Agreement, 2013
Reinsurance Disclosures [Abstract]
Losses incurred - Ceded			0		(6,060,000)
Premiums Written and Earned [Abstract]
Ceded premiums written, net of profit commission			(69,410,000)		(11,355,000)
Ceded premiums earned, net of profit commission			(11,568,000)		35,999,000
Ceded losses incurred			0		6,060,000
Ceding commissions			(11,568,000)		10,235,000
Profit commission			11,568,000		62,525,000
Quota Share Reinsurance Agreement, 2015
Reinsurance Disclosures [Abstract]
Losses incurred - Ceded		(7,432,000)	(4,236,000)	(22,015,000)	(4,236,000)
Effects of Reinsurance [Line Items]
Contingent termination fee	$ 0
Threshold for private mortgage insurer eligibility requirements for termination election (less than)	90.00%
Quota share for all policies covered	30.00%
Ceding commission, percentage	20.00%
Loss ratio threshold for profit commissions	60.00%
Premiums Written and Earned [Abstract]
Ceded premiums written, net of profit commission		31,707,000	22,626,000	93,334,000	22,626,000
Ceded premiums earned, net of profit commission		31,707,000	22,626,000	93,334,000	22,626,000
Ceded losses incurred		7,432,000	4,236,000	22,015,000	4,236,000
Ceding commissions		12,137,000	9,195,000	35,659,000	9,195,000
Profit commission		28,981,000	$ 23,347,000	84,963,000	$ 23,347,000
Reinsurance recoverable on loss reserves		$ 27,000,000		$ 27,000,000		$ 11,000,000