Losses and Loss Adjustment Reserve - Additional Information (Detail)	9 Months Ended
	Sep. 30, 2015 USD ($) Reinsurer	Dec. 31, 2014 USD ($)
Reinsurance Premiums for Insurance Companies, by Product Segment [Line Items]
Ceded rate of premiums under insurance program	100.00%
Premiums written net	$ 468,750,000
Ceded unpaid loss	37,200,000
The reinsurance recoverable	367,000,000
Prepaid reinsurance premiums	329,777,000	$ 320,586,000
Increase (Decrease) in Loss and Loss Adjustment Expense Reserve	0
Reserve for losses and loss adjustment expense	$ 37,200,000
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	102
Private Passenger Auto Liability
Reinsurance Premiums for Insurance Companies, by Product Segment [Line Items]
Ceded unpaid loss	48,254
Reinsurance recoverable, incurred but not reported claims	39,424
Other Liability
Reinsurance Premiums for Insurance Companies, by Product Segment [Line Items]
Ceded unpaid loss	$ 756
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	30.80%
Premiums written net	$ 467,800,000
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	$ 900,000