Loss And Loss Adjustment Expense Reserves (Schedule Of Present Value Of The Probability-Weighted Future Claim Payments And Recoveries) (Detail) (USD $) In Millions, unless otherwise specified	Jun. 30, 2012	Dec. 31, 2011
Loss And Loss Adjustment Expense Reserves [Line Items]
Insurance loss recoverable	$ (3,212)	$ (3,046)
Loss Reserves (Claim Liability) [Member] | Classified [Member]
Loss And Loss Adjustment Expense Reserves [Line Items]
Loss and loss adjustment expense reserves	755	781
LAE Reserves [Member] | Classified [Member]
Loss And Loss Adjustment Expense Reserves [Line Items]
Loss and loss adjustment expense reserves	80	55
Loss And LAE Reserves [Member]
Loss And Loss Adjustment Expense Reserves [Line Items]
Loss and loss adjustment expense reserves	835	836
Loss And LAE Reserves [Member] | Classified [Member]
Loss And Loss Adjustment Expense Reserves [Line Items]
Loss and loss adjustment expense reserves	835	836
Insurance Loss Recoverable [Member]
Loss And Loss Adjustment Expense Reserves [Line Items]
Insurance claim loss recoverable	(2,200)
Insurance Loss Recoverable [Member] | Classified [Member]
Loss And Loss Adjustment Expense Reserves [Line Items]
Insurance claim loss recoverable	(3,185)	(3,032)
LAE insurance loss recoverable	(27)	(14)
Insurance loss recoverable	(3,212)	(3,046)
Reinsurance recoverable	14	15
Reinsurance recoverable on paid losses		1
Reinsurance recoverable on paid and unpaid losses	$ 14	$ 16