Loss And Loss Adjustment Expense Reserves (Schedule Of Loss And Loss Adjustment Expenses Reserves) (Detail) - USD ($) $ in Millions		3 Months Ended
		Mar. 31, 2017	Mar. 31, 2016
Loss And Loss Adjustment Expense Reserves [Line Items]
Gross loss and LAE reserve, beginning balance		$ 541
Changes in unearned premium revenue		45	$ 81
Gross loss and LAE reserve, ending balance		559
Loss And Lae Reserves [Member]
Loss And Loss Adjustment Expense Reserves [Line Items]
Gross loss and LAE reserve, beginning balance		541
Loss payments for cases with reserves	[1]	(804)
Accretion of claim liability discount		1
Changes in discount rates		5
Changes in assumptions		96
Changes in unearned premium revenue		4
Changes in LAE		2
Other	[2]	714
Gross loss and LAE reserve, ending balance		$ 559

[1] Includes payments made to satisfy the Zohar II Claim.

[2] Primarily changes in the amount to satisfy the Zohar II Claim.