Loss And Loss Adjustment Expense Reserves (Schedule Of Loss And Loss Adjustment Expenses Reserves) (Detail) - USD ($) $ in Millions		9 Months Ended
		Sep. 30, 2017	Sep. 30, 2016
Loss And Loss Adjustment Expense Reserves [Line Items]
Gross loss and LAE reserve, beginning balance		$ 541
Changes in unearned premium revenue		149	$ 197
Gross loss and LAE reserve, ending balance		818
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]	(1,057)
Accretion of claim liability discount		7
Changes in discount rates		8
Changes in assumptions		498
Changes in unearned premium revenue		(32)
Changes in LAE		9
Other	[2]	844
Gross loss and LAE reserve, ending balance		$ 818

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

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