Loss And Loss Adjustment Expense Reserves (Schedule Of Insurance Loss Recoverable And Changes In Recoveries On Unpaid Losses) (Detail) $ in Millions	6 Months Ended
	Jun. 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	(49)
Accretion of Recoveries	6
Changes in Discount Rates	10
Changes in Assumptions	(25)
Changes in LAE Recoveries	(5)
Other	20	[1]
Gross Reserve ending balance, Insurance loss recoverable	483
Gross Reserve ending balance, Total	540
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	(49)
Accretion of Recoveries	5
Changes in Discount Rates	9
Changes in Assumptions	(6)
Changes in LAE Recoveries	0
Other	20	[2]
Gross Reserve ending balance, Insurance loss recoverable	483
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	(19)	[2]
Changes in LAE Recoveries	(5)	[2]
Other	0
Gross Reserve ending balance, Recoveries on unpaid losses	$ 57	[2]

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

[2] As of June 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.