Loss And Loss Adjustment Expense Reserves (Schedule Of Loss And Loss Adjustment Expenses Reserves) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended				3 Months Ended
	Mar. 31, 2012	Mar. 31, 2011	Mar. 31, 2012 Non Variable Interest Entities [Member]	Dec. 31, 2011 Non Variable Interest Entities [Member]	Mar. 31, 2012 Loss And LAE Reserves [Member]
Loss And Loss Adjustment Expense Reserves [Line Items]
Gross Loss and LAE Reserve as of December 31, 2011			$ 867	$ 836	$ 836
Loss Payments for Cases with Reserves					(114)
Accretion of Claim Liability Discount					3
Changes in Discount Rates					(22)
Changes in Timing of Payments					34
Changes in Amount of Net Payments					(1)
Changes in Assumptions					78
Changes in Unearned Premium Revenue	(149)	(127)			(4)
Change in LAE Reserves	(31)	119			57
Gross Loss and LAE Reserve as of March 31, 2012			$ 867	$ 836	$ 867