REINSURANCE (Detail) (USD $)	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Reinsurance recoveries on losses and loss expenses incurred	$ 1,100,000,000	$ 1,000,000,000	$ 800,000,000
Reinsurance Receivables	3,900,000,000	3,800,000,000
Reinsurance Receivables Including Paid Losses And Loss Expenses	220,000,000	171,300,000
Reinsurance Receivables, Incurred but Not Reported Claims	3,654,948,000	3,671,887,000
Allowance for Reinsurance balances receivable and unpaid losses and loss expenses recoverable	99,200,000	121,900,000
Collateral Held Related To Reinsurance Recoverables	1,700,000,000
Reinsurance Recoverables	55,300,000	68,100,000
Uncollectible Reinsurance Receivables	$ 43,900,000	$ 53,800,000
Total unpaid loss and loss expense recoverable and reinsurance balances receivable outstanding, excluding collateral held, percent	92.20%