Loss And Loss Adjustment Expense Reserves (Schedule Of Loss And Loss Adjustment Expenses Reserves) (Detail) - USD ($) $ in Millions		6 Months Ended
		Jun. 30, 2016	Jun. 30, 2015
Loss And Loss Adjustment Expense Reserves [Line Items]
Changes in unearned premium revenue		$ 194	$ 184
Loss And Lae Reserves [Member]
Loss And Loss Adjustment Expense Reserves [Line Items]
Gross loss and LAE reserve, beginning balance		516
Loss payments for cases with reserves		(47)
Accretion of claim liability discount		5
Changes in discount rates		32
Changes in assumptions		35
Changes in unearned premium revenue		(12)
Changes in LAE		14
Other	[1]	3
Gross loss and LAE reserve, ending balance		$ 546

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