Loss And Loss Adjustment Expense Reserves (Schedule Of Insurance Loss Recoverable And Changes In Recoveries On Unpaid Losses) (Detail) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2018		Dec. 31, 2017
Loss And Loss Adjustment Expense Recoveries [Line Items]
Gross Reserve beginning balance, Total		$ 546		$ 583
Collections for Cases		(56)		(124)
Accretion of Recoveries		26		11
Changes in Discount Rates		(14)		3
Changes in Assumptions		1,091		68
Changes in LAE Recoveries		(8)		(1)
Other	[1]	(2)		6
Gross Reserve ending balance, Total		1,583		546
Insurance Loss Recoverable [Member]
Loss And Loss Adjustment Expense Recoveries [Line Items]
Gross Reserve beginning balance, Insurance loss recoverable		511		504
Collections for Cases		(56)		(124)
Accretion of Recoveries		25		10
Changes in Discount Rates		(13)		2
Changes in Assumptions		1,099	[2]	113
Changes in LAE Recoveries		0		0
Other	[1]	(2)		6
Gross Reserve ending balance, Insurance loss recoverable		1,564		511
Recoveries On Unpaid Losses [Member]
Loss And Loss Adjustment Expense Recoveries [Line Items]
Gross Reserve beginning balance,Recoveries on unpaid losses		35	[3]	79	[4]
Collections for Cases		0		0
Accretion of Recoveries	[3]	1		1	[4]
Changes in Discount Rates	[3]	(1)		1	[4]
Changes in Assumptions	[3]	(8)		(45)	[4]
Changes in LAE Recoveries	[3]	(8)		(1)	[4]
Other		0		0	[1],[4]
Gross Reserve ending balance, Recoveries on unpaid losses	[3]	$ 19		$ 35

[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 December 31, 2018 and December 31, 2017, excludes Puerto Rico recoveries, which have been netted against reserves.

[4] Excludes Zohar II recoveries, which have been netted against reserves.