Supplementary Insurance Information (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Supplementary Insurance Information, by Segment [Line Items]
Premium Revenue	$ 468,465	$ 504,143	$ 268,519
Benefits, Claims, Losses And Settlement Expenses	264,003	275,368	137,561
Amortization of Deferred Policy Acquisition Costs	114,317	86,170	57,051
Net Written Premium	470,940	501,244	273,181
Commercial Lines Segment
Supplementary Insurance Information, by Segment [Line Items]
Deferred Policy Acquisition Costs	19,755	20,784	21,249
Future Policy Benefits, Losses, Claims And Loss Expenses	458,645	524,607	579,621
Unearned Premiums	94,698	100,027	102,118
Other Policy and Benefits Payable	0
Premium Revenue	190,727	199,304	211,165
Benefits, Claims, Losses And Settlement Expenses	74,996	97,530	117,586
Amortization of Deferred Policy Acquisition Costs	42,361	43,821	45,015
Net Written Premium	184,911	197,526	212,965
Personal Lines Segment
Supplementary Insurance Information, by Segment [Line Items]
Deferred Policy Acquisition Costs	28,381	31,900
Future Policy Benefits, Losses, Claims And Loss Expenses	127,350	94,359
Unearned Premiums	157,464	169,669
Premium Revenue	236,170	253,048
Benefits, Claims, Losses And Settlement Expenses	174,933	163,986
Amortization of Deferred Policy Acquisition Costs	61,416	31,291
Net Written Premium	226,228	254,035
Reinsurance Operations
Supplementary Insurance Information, by Segment [Line Items]
Deferred Policy Acquisition Costs	9,765	3,833	3,989
Future Policy Benefits, Losses, Claims And Loss Expenses	65,047	61,081	95,851
Unearned Premiums	34,822	16,589	18,697
Premium Revenue	41,568	51,791	57,354
Benefits, Claims, Losses And Settlement Expenses	14,074	13,852	19,975
Amortization of Deferred Policy Acquisition Costs	10,540	11,058	12,036
Net Written Premium	$ 59,801	$ 49,683	$ 60,216