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, 2018 USD ($)
Loss And Loss Adjustment Expense Recoveries [Line Items]
Gross Reserve beginning balance, Total	$ 546
Collections for Cases	(42)
Accretion of Recoveries	15
Changes in Discount Rates	(30)
Changes in Assumptions	1,076
Changes in LAE Recoveries	(6)
Other	4	[1]
Gross Reserve ending balance, Total	1,563
Insurance Loss Recoverable [Member]
Loss And Loss Adjustment Expense Recoveries [Line Items]
Gross Reserve beginning balance, Insurance loss recoverable	511
Collections for Cases	(42)
Accretion of Recoveries	14
Changes in Discount Rates	(29)
Changes in Assumptions	1,084	[2]
Changes in LAE Recoveries	0
Other	4	[1]
Gross Reserve ending balance, Insurance loss recoverable	1,542
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	1	[3]
Changes in Discount Rates	(1)	[3]
Changes in Assumptions	(8)	[3]
Changes in LAE Recoveries	(6)	[3]
Other	0
Gross Reserve ending balance, Recoveries on unpaid losses	$ 21	[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 September 30, 2018 and December 31, 2017, excludes Puerto Rico recoveries, which have been netted against reserves.