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, 2018 USD ($)
Loss And Loss Adjustment Expense Recoveries [Line Items]
Gross Reserve beginning balance, Total	$ 546
Collections for Cases	(29)
Accretion of Recoveries	6
Changes in Discount Rates	(19)
Changes in Assumptions	884
Changes in LAE Recoveries	0
Other	4	[1]
Gross Reserve ending balance, Total	1,392
Insurance Loss Recoverable [Member]
Loss And Loss Adjustment Expense Recoveries [Line Items]
Gross Reserve beginning balance, Insurance loss recoverable	511
Collections for Cases	(29)
Accretion of Recoveries	6
Changes in Discount Rates	(18)
Changes in Assumptions	885	[2]
Changes in LAE Recoveries	0
Other	4	[1]
Gross Reserve ending balance, Insurance loss recoverable	1,359
Recoveries On Unpaid Losses [Member]
Loss And Loss Adjustment Expense Recoveries [Line Items]
Gross Reserve beginning balance,Recoveries on unpaid losses	35	[3]
Collections for Cases	0
Accretion of Recoveries	0
Changes in Discount Rates	(1)	[3]
Changes in Assumptions	(1)	[3]
Changes in LAE Recoveries	0	[3]
Other	0
Gross Reserve ending balance, Recoveries on unpaid losses	$ 33	[3]

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

[2] Includes amounts which have been paid and are expected to be recovered in the future.

[3] As of June 30, 2018 and December 31, 2017, excludes Puerto Rico recoveries, which have been netted against reserves.