Loss And Loss Adjustment Expense Reserves (Schedule Of Insurance Loss Recoverable And Changes In Recoveries On Unpaid Losses) (Details) (Insurance Loss Recoverable And Changes In Recoveries On Unpaid Losses [Member], USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010
Loss And Loss Adjustment Expense Reserves [Line Items]
Gross Reserve as of beginning balance, Total	$ 3,427	$ 3,276
Accounting Transition Adjustment		(809)	[1]
Collections for Cases with Recoveries	(101)	(81)
Accretion of Recoveries	73	51
Changes in Discount Rates	117	(11)
Changes in Timing of Collections		33
Changes in Amount of Collections	(227)	(64)
Changes in Assumptions	307	1,049
Changes in LAE Recoveries	12	(17)
Gross Reserve as of ending balance, Total	3,608	3,427
Insurance Loss Recoverable [Member]
Loss And Loss Adjustment Expense Reserves [Line Items]
Gross Insurance Loss Recoverable, beginning balance	2,531	2,445
Accounting Transition Adjustment		(594)	[1]
Collections for Cases with Recoveries	(101)	(81)
Accretion of Recoveries	57	36
Changes in Discount Rates	49	(10)
Changes in Timing of Collections		33
Changes in Amount of Collections	(227)	(56)
Changes in Assumptions	723	790
Changes in LAE Recoveries	14	(32)
Gross Insurance Loss Recoverable, ending balance	3,046	2,531
Recoveries On Unpaid Losses [Member]
Loss And Loss Adjustment Expense Reserves [Line Items]
Gross Reserve as of beginning balance, Recoveries on Unpaid Losses	896	831
Accounting Transition Adjustment		(215)	[1]
Accretion of Recoveries	16	15
Changes in Discount Rates	68	(1)
Changes in Amount of Collections		(8)
Changes in Assumptions	(416)	259
Changes in LAE Recoveries	(2)	15
Gross Reserve as of ending balance, Recoveries on Unpaid Losses	$ 562	$ 896

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