Loss And Loss Adjustment Expense Reserves (Schedule Of Insurance Loss Recoverable And Changes In Recoveries On Unpaid Losses) (Detail) (Insurance Loss Recoverable And Changes In Recoveries On Unpaid Losses [Member], USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2013
Insurance Loss Recoverable and Recoveries On Unpaid Losses [Line Items]
Collections for Cases with Recoveries	$ (9)
Accretion of Recoveries	12
Changes in Discount Rates	(9)
Changes in Timing of Collections
Changes in Amount of Collections	(53)
Changes in Assumptions	244
Changes in LAE Recoveries	4,166
Gross Reserve beginning balance, Total	3,980
Gross Reserve ending balance, Total	4,166
Insurance Loss Recoverable [Member]
Insurance Loss Recoverable and Recoveries On Unpaid Losses [Line Items]
Collections for Cases with Recoveries	(9)
Accretion of Recoveries	11
Changes in Discount Rates	(4)
Changes in Timing of Collections
Changes in Amount of Collections	(53)
Changes in Assumptions	285
Changes in LAE Recoveries	3,877
Gross Reserve beginning balance, Insurance loss recoverable	3,648
Gross Reserve ending balance, Insurance loss recoverable	3,877
Recoveries On Unpaid Losses [Member]
Insurance Loss Recoverable and Recoveries On Unpaid Losses [Line Items]
Accretion of Recoveries	1
Changes in Discount Rates	(5)
Changes in Timing of Collections
Changes in Assumptions	(41)
Changes in LAE Recoveries	289
Gross Reserve beginning balance, Recoveries on unpaid losses	332
Gross Reserve ending balance, Recoveries on unpaid losses	$ 289