Valuation and Qualifying Accounts (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Allowance for Reinsurance Recoverable
Valuation and Qualifying Accounts Disclosure [Line Items]
Beginning Balance
Charged to Costs and Expenses
Charged to Other Accounts-Describe
Deductions-Describe
Ending Balance
Allowance for Uncollectible Premiums Receivable
Valuation and Qualifying Accounts Disclosure [Line Items]
Beginning Balance	1,064	974	3,412
Charged to Costs and Expenses	1,096	769	918
Charged to Other Accounts-Describe
Deductions-Describe	799	679	3,356
Ending Balance	$ 1,361	$ 1,064	$ 974