Valuation and Qualifying Accounts and Reserves (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Allowance for Loans and Leases Receivable
Valuation and Qualifying Accounts Disclosure [Line Items]
Charged (Credited) to Other Accounts	$ 0	$ 0	$ 0
Other Deductions	0	0	0
Allowance for Loan and Lease Losses, Real Estate
Valuation and Qualifying Accounts Disclosure [Line Items]
Charged (Credited) to Other Accounts	0	0	0
Other Deductions	0	0	0
Allowance for Doubtful Accounts
Valuation and Qualifying Accounts Disclosure [Line Items]
Balance at Beginning of Period	1,646	1,518	1,782
Charged (Credited) to Costs and Expenses	282	128	(264)
Charged (Credited) to Other Accounts	0	0	0
Other Deductions	0	0	0
Balance at End of Period	1,928	1,646	1,518
Valuation Allowance of Deferred Tax Assets
Valuation and Qualifying Accounts Disclosure [Line Items]
Charged (Credited) to Other Accounts	0	0	0
Other Deductions	0	0	0
Allowance for Reinsurance Recoverable
Valuation and Qualifying Accounts Disclosure [Line Items]
Balance at Beginning of Period	9,675	9,350	9,010
Charged (Credited) to Costs and Expenses	(1,635)	325	340
Charged (Credited) to Other Accounts	0	0	0
Other Deductions	0	0	0
Balance at End of Period	$ 8,040	$ 9,675	$ 9,350