Valuation and Qualifying Accounts (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2011
Allowance for uncollectable reinsurance
Valuation and Qualifying Accounts Disclosure [Line Items]
Balance at January 1, 2011	$ 12,970
Charged (Credited) to Costs and Expenses	50
Charged to Other Accounts
Deductions (Describe)
Balance at December 31, 2011	13,020
Valuation allowance in deferred taxes
Valuation and Qualifying Accounts Disclosure [Line Items]
Balance at January 1, 2011	2,185
Charged (Credited) to Costs and Expenses	(1,943)
Charged to Other Accounts
Deductions (Describe)
Balance at December 31, 2011	$ 242