Loss And Loss Adjustment Expense Reserves (Schedule Of Total Estimated Recoveries From Ineligible Mortgage Loans) (Details) (Ineligible Mortgage Loans [Member], USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010
Ineligible Mortgage Loans [Member]
Loss And Loss Adjustment Expense Reserves [Line Items]
Total Estimated Recoveries from Ineligible loans as of Beginning Balance	$ 2,517	$ 1,575
Accretion of Future Collections	65	51
Changes in Discount Rates	35	21
Recoveries (Collections)	(86)	(67)
Changes in Amount of Collections	29
Changes in Assumptions	559	937
Total Estimated Recoveries from Ineligible loans as of Ending Balance	$ 3,119	$ 2,517