Loss And Loss Adjustment Expense Reserves (Schedule Of Expenses Related To Remedial Actions For Insured Obligations) (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011
Loss And Loss Adjustment Expense Reserves [Line Items]
Loss adjustment expense incurred, net			$ 159
Remedial Actions For Insured Obligations [Member]
Loss And Loss Adjustment Expense Reserves [Line Items]
Loss adjustment expense incurred, gross	6	30	81	45
Loss adjustment expense incurred, net	$ 6	$ 30	$ 81	$ 45