Liability for Unpaid Claims and Claim Adjustment Expenses - Schedule of Reconciliation of Net Incurred and Paid Claims Development Tables to Liability for Claims and Claim Adjustment Expenses in Consolidated Statement of Financial Position (Detail) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Net outstanding liabilities
Liabilities for unpaid claims and claim adjustment expenses, net of reinsurance	$ 963,752
Reinsurance recoverable on unpaid claims
Total reinsurance recoverable on unpaid claims	250,417
Insurance lines other than short-duration	215,966
Unallocated claims adjustment expenses	51,159
Total claim adjustment expenses	267,125
Total gross liability for unpaid claims and claim adjustment expense	1,481,294	$ 1,390,561
Credit
Net outstanding liabilities
Liabilities for unpaid claims and claim adjustment expenses, net of reinsurance	16,615
Reinsurance recoverable on unpaid claims
Total reinsurance recoverable on unpaid claims	11,025
Auto Liability
Net outstanding liabilities
Liabilities for unpaid claims and claim adjustment expenses, net of reinsurance	448,736
Reinsurance recoverable on unpaid claims
Total reinsurance recoverable on unpaid claims	11,731
Non-Auto Liability
Net outstanding liabilities
Liabilities for unpaid claims and claim adjustment expenses, net of reinsurance	256,558
Reinsurance recoverable on unpaid claims
Total reinsurance recoverable on unpaid claims	37,234
Homeowners
Net outstanding liabilities
Liabilities for unpaid claims and claim adjustment expenses, net of reinsurance	72,895
Reinsurance recoverable on unpaid claims
Total reinsurance recoverable on unpaid claims	2,993
Commercial Multi-Peril
Net outstanding liabilities
Liabilities for unpaid claims and claim adjustment expenses, net of reinsurance	92,695
Reinsurance recoverable on unpaid claims
Total reinsurance recoverable on unpaid claims	3,381
Short Tail Property
Net outstanding liabilities
Liabilities for unpaid claims and claim adjustment expenses, net of reinsurance	33,801
Reinsurance recoverable on unpaid claims
Total reinsurance recoverable on unpaid claims	3,124
Health
Net outstanding liabilities
Liabilities for unpaid claims and claim adjustment expenses, net of reinsurance	40,361
Reinsurance recoverable on unpaid claims
Total reinsurance recoverable on unpaid claims	173,329
Other
Net outstanding liabilities
Liabilities for unpaid claims and claim adjustment expenses, net of reinsurance	2,091
Reinsurance recoverable on unpaid claims
Total reinsurance recoverable on unpaid claims	$ 7,600