Reconciliation of Net Incurred and Paid Claims Development Tables to Liability for Unpaid Losses and Loss Adjustment Expenses in Consolidated Balance Sheets (Detail) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability [Line Items]
Net outstanding liabilities	$ 490,558
Reinsurance recoverable on unpaid claims	128,692
Total other outstanding liabilities	31,792
Total gross liability for unpaid losses and loss adjustment expenses	651,042	$ 680,047	$ 675,472	$ 779,466
Commercial Lines Segment
Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability [Line Items]
Ceded Allowance	8,040
Unallocated claims adjustment expenses	17,795
Purchase accounting adjustment	(2,000)
Loss Clearing	(910)
Commercial Lines Segment | Property Insurance
Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability [Line Items]
Net outstanding liabilities	41,052
Reinsurance recoverable on unpaid claims	6,439
Commercial Lines Segment | Casualty Insurance
Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability [Line Items]
Net outstanding liabilities	311,274
Reinsurance recoverable on unpaid claims	76,956
Personal Lines Segment
Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability [Line Items]
Fronted business ceded to Assurant	3,748
Unallocated claims adjustment expenses	4,685
Loss Clearing	(68)
Personal Lines Segment | Property Insurance
Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability [Line Items]
Net outstanding liabilities	30,424
Reinsurance recoverable on unpaid claims	39,708
Personal Lines Segment | Casualty Insurance
Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability [Line Items]
Net outstanding liabilities	43,500
Reinsurance recoverable on unpaid claims	5,352
Reinsurance Operations
Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability [Line Items]
Unallocated claims adjustment expenses	646
Other	(144)
Reinsurance Operations | Property Insurance
Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability [Line Items]
Net outstanding liabilities	42,021
Reinsurance Operations | Casualty Insurance
Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability [Line Items]
Net outstanding liabilities	22,287
Reinsurance recoverable on unpaid claims	$ 237