Loss And Loss Adjustment Expense Reserves (Schedule Of Insurance Loss Recoverable And Changes In Recoveries On Unpaid Losses) (Detail) (USD $) In Millions, unless otherwise specified	6 Months Ended
	Jun. 30, 2013
Loss And Loss Adjustment Expense Recoveries [Line Items]
Gross Reserve beginning balance, Total	$ 3,980
Gross Reserve ending balance, Total	1,304
Collections for Cases with Recoveries	(2,852)
Accretion of Recoveries	15
Changes in Discount Rates	(44)
Changes in Timing of Collections	0
Changes in Amount of Collections	(1)
Changes in Assumptions	237
Changes in LAE Recoveries	(31)
Insurance Loss Recoverable [Member]
Loss And Loss Adjustment Expense Recoveries [Line Items]
Gross Reserve beginning balance, Insurance loss recoverable	3,648
Gross Reserve ending balance, Insurance loss recoverable	907
Collections for Cases with Recoveries	(2,852)
Accretion of Recoveries	13
Changes in Discount Rates	(22)
Changes in Timing of Collections	0
Changes in Amount of Collections	(1)
Changes in Assumptions	154
Changes in LAE Recoveries	(33)
Recoveries On Unpaid Losses [Member]
Loss And Loss Adjustment Expense Recoveries [Line Items]
Gross Reserve beginning balance,Recoveries on unpaid losses	332
Gross Reserve ending balance, Recoveries on unpaid losses	397
Collections for Cases with Recoveries	0
Accretion of Recoveries	2
Changes in Discount Rates	(22)
Changes in Timing of Collections	0
Changes in Amount of Collections	0
Changes in Assumptions	83
Changes in LAE Recoveries	$ 2