Loss And Loss Adjustment Expense Reserves (Schedule Of Expenses Related To Remedial Actions For Insured Obligations) (Details) (USD $) In Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2011	Sep. 30, 2010	Sep. 30, 2011	Sep. 30, 2010
Loss And Loss Adjustment Expense Reserves [Line Items]
Loss adjustment expense incurred, net	$ 190	$ (20)	$ 204	$ 122
Remedial Actions For Insured Obligations [Member]
Loss And Loss Adjustment Expense Reserves [Line Items]
Loss adjustment expense incurred, gross	31	14	76	30
Loss adjustment expense incurred, net	$ 31	$ 14	$ 76	$ 29