Losses and Loss Adjustment Reserve - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2015 USD ($) Reinsurer	Dec. 31, 2014 USD ($)	Sep. 30, 2015
Reinsurance Premiums for Insurance Companies, by Product Segment [Line Items]
Ceded rate of premiums under insurance program	100.00%
Premiums written net	$ 599,807,000
Ceded unpaid loss	32,000,000	$ 13,000,000
The reinsurance recoverable	341,600,000	333,600,000
Prepaid reinsurance premiums	309,643,000	320,586,000
Increase (Decrease) in Loss and Loss Adjustment Expense Reserve	0
Reserve for losses and loss adjustment expense	$ 32,000,000	13,000,000
Number of reinsurers | Reinsurer	3
Homeowners
Reinsurance Premiums for Insurance Companies, by Product Segment [Line Items]
Ceded unpaid loss	$ 8,698
Reinsurance recoverable, incurred but not reported claims	10,335
Private Passenger Auto Liability
Reinsurance Premiums for Insurance Companies, by Product Segment [Line Items]
Ceded unpaid loss	16,132
Reinsurance recoverable, incurred but not reported claims	14,383
Other Liability
Reinsurance Premiums for Insurance Companies, by Product Segment [Line Items]
Ceded unpaid loss	4,179
Reinsurance recoverable, incurred but not reported claims	$ 8,456
Wright Flood
Reinsurance Premiums for Insurance Companies, by Product Segment [Line Items]
Ceded rate of premiums under insurance program	100.00%
Expenses and allowance rate received in premiums	30.90%		30.80%
Premiums written net	$ 598,400,000	439,100,000
Wright Flood | Quota Share Agreement
Reinsurance Premiums for Insurance Companies, by Product Segment [Line Items]
Effective cedes rate under quota share agreement	100.00%
Commission rate, percent of ceded written premiums	30.50%
Wright Flood | Quota Share Agreement | Ceded Credit Risk, Concentrated Credit Risk
Reinsurance Premiums for Insurance Companies, by Product Segment [Line Items]
Ceded amount	$ 1,400,000	$ 800,000