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, 2016		Dec. 31, 2015
Loss And Loss Adjustment Expense Recoveries [Line Items]
Gross Reserve beginning balance, Total		$ 677		$ 680
Collections for Cases with Recoveries		(69)		(74)
Accretion of Recoveries		6		10
Changes in Discount Rates		(14)		(1)
Changes in Assumptions		52		94
Changes in LAE Recoveries		3		5
Other		(72)	[1]	(37)	[2]
Gross Reserve ending balance, Total		583		677
Insurance Loss Recoverable [Member]
Loss And Loss Adjustment Expense Recoveries [Line Items]
Gross Reserve beginning balance, Insurance loss recoverable		577		533
Collections for Cases with Recoveries		(69)		(74)
Accretion of Recoveries		5		8
Changes in Discount Rates		(17)		1
Changes in Assumptions		86		140
Changes in LAE Recoveries		(6)		6
Other	[2]	(72)		(37)
Gross Reserve ending balance, Insurance loss recoverable		504		577
Recoveries On Unpaid Losses [Member]
Loss And Loss Adjustment Expense Recoveries [Line Items]
Gross Reserve beginning balance,Recoveries on unpaid losses		100		147
Collections for Cases with Recoveries	[3]	0		0
Accretion of Recoveries	[3]	1		2
Changes in Discount Rates	[3]	3		(2)
Changes in Assumptions	[3]	(34)		(46)
Changes in LAE Recoveries	[3]	9		(1)
Other	[2],[3]	0		0
Gross Reserve ending balance, Recoveries on unpaid losses		$ 79		$ 100

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

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

[3] Excludes Puerto Rico and Zohar II recoveries, which have been netted against reserves.