Loss And Loss Adjustment Expense Reserves (Schedule Of Loss And Loss Adjustment Expenses Reserves) (Detail) - USD ($) $ in Millions		6 Months Ended
		Jun. 30, 2017	Jun. 30, 2016
Loss And Loss Adjustment Expense Reserves [Line Items]
Gross loss and LAE reserve, beginning balance		$ 541
Changes in unearned premium revenue		97	$ 194
Gross loss and LAE reserve, ending balance		714
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]	(820)
Accretion of claim liability discount		4
Changes in discount rates		2
Changes in assumptions		269
Changes in unearned premium revenue		(27)
Changes in LAE		12
Other	[2]	733
Gross loss and LAE reserve, ending balance		$ 714

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

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