Loss And Loss Adjustment Expense Reserves (Schedule Of Insurance Loss Recoverable And Changes In Recoveries On Unpaid Losses) (Detail) $ in Millions	9 Months Ended
	Sep. 30, 2017 USD ($)
Loss And Loss Adjustment Expense Recoveries [Line Items]
Gross Reserve beginning balance, Insurance loss recoverable	$ 504
Gross Reserve beginning balance, Total	583
Collections for Cases with Recoveries	(56)
Accretion of Recoveries	8
Changes in Discount Rates	8
Changes in Assumptions	91
Changes in LAE Recoveries	(5)
Other	16	[1]
Gross Reserve ending balance, Insurance loss recoverable	611
Gross Reserve ending balance, Total	645
Insurance Loss Recoverable [Member]
Loss And Loss Adjustment Expense Recoveries [Line Items]
Gross Reserve beginning balance, Insurance loss recoverable	504
Collections for Cases with Recoveries	(56)
Accretion of Recoveries	7
Changes in Discount Rates	7
Changes in Assumptions	133
Changes in LAE Recoveries	0
Other	16	[2]
Gross Reserve ending balance, Insurance loss recoverable	611
Recoveries On Unpaid Losses [Member]
Loss And Loss Adjustment Expense Recoveries [Line Items]
Gross Reserve beginning balance,Recoveries on unpaid losses	79	[2]
Collections for Cases with Recoveries	0
Accretion of Recoveries	1
Changes in Discount Rates	1	[2]
Changes in Assumptions	(42)	[2]
Changes in LAE Recoveries	(5)	[2]
Other	0
Gross Reserve ending balance, Recoveries on unpaid losses	$ 34	[2]

[1] Primarily changes in amount and timing of collections.

[2] As of September 30, 2017 and December 31, 2016, excludes Puerto Rico recoveries, and as of December 31, 2016, the Zohar II recoveries, which have been netted against reserves.