Reinsurance (Details) - 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
Premiums Written [Abstract]
Direct									$ 366,668	$ 343,200	$ 314,784
Ceded on direct									(128,338)	(118,942)	(112,967)
Net direct									238,330	224,258	201,817
Assumed									16,885	39,188	54,692
Ceded on assumed									(562)	(1,275)	(2,825)
Net assumed									16,323	37,913	51,867
Net									254,653	262,171	253,684
Premium Earned [Abstract]
Direct									370,499	342,656	313,842
Ceded on direct									(128,135)	(117,973)	(111,057)
Net direct									242,364	224,683	202,785
Assumed									21,533	38,219	52,783
Ceded on assumed									(562)	(1,275)	(2,825)
Net assumed									20,971	36,944	49,958
Net	$ 65,995	$ 65,445	$ 65,449	$ 66,446	$ 68,933	$ 65,947	$ 62,905	$ 63,842	263,335	261,627	252,743
Net losses and loss expenses incurred reduced by ceded reinsurance recoveries									75,581	105,891	107,321
Net losses and loss expense incurred from reinsurance assumed from non-affiliates									13,492	20,288	$ 17,696
Components of reinsurance recoverable [Abstract]
Case unpaid losses, net of valuation allowance	120,320				143,403				120,320	143,403
Incurred but not reported unpaid losses and loss expenses	90,578				66,325				90,578	66,325
Paid losses and loss expenses	2,452				6,910				2,452	6,910
Unearned premiums	2,538				3,583				2,538	3,583
Reinsurance recoverable	$ 215,888				$ 220,221				$ 215,888	$ 220,221