Loss And Loss Adjustment Expense Reserves (Schedule Of Loss And Loss Adjustment Expense Reserves) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010		Dec. 31, 2009
Loss And Loss Adjustment Expense Reserves [Line Items]
Unearned Premium Revenue	$ (624)	$ (635)		$ (906)
Change in LAE Reserves	293	81		(196)
Non Variable Interest Entities [Member]
Loss And Loss Adjustment Expense Reserves [Line Items]
Accounting Transition Adjustment		150	[1]
Gross Loss and LAE Reserves ending balance	836	1,129
Loss And LAE Reserves [Member]
Loss And Loss Adjustment Expense Reserves [Line Items]
Gross Loss and LAE Reserves beginning balance	1,129	1,580
Accounting Transition Adjustment		(364)	[2]
Loss Payments for Cases with Reserves	(523)	(1,046)
Accretion of Claim Liability Discount	14	8
Changes in Discount Rates	(20)	28
Changes in Timing of Payments	38	39
Changes in Amount of Net Payments		(3)
Changes in Assumptions	193	914
Unearned Premium Revenue	20	(28)
Change in LAE Reserves	(15)	1
Gross Loss and LAE Reserves ending balance	$ 836	$ 1,129

[1] Reflects the adoption of the accounting principles for the consolidation of VIEs.

[2] Reflects the adoption of the accounting principles for the consolidation of variable interest entities.