Loss And Loss Adjustment Expense Reserves (Schedule Of Loss And Loss Adjustment Expenses Reserves) (Detail) - USD ($) $ in Millions		3 Months Ended
		Mar. 31, 2016	Mar. 31, 2015
Loss And Loss Adjustment Expense Reserves [Line Items]
Changes in unearned premium revenue		$ 81	$ 83
Changes in LAE reserves		9	$ (6)
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		(8)
Accretion of claim liability discount		2
Changes in discount rates		18
Changes in assumptions		12
Changes in unearned premium revenue		(12)
Changes in LAE reserves		3
Other	[1]	(6)
Gross loss and LAE reserve, ending balance		$ 525

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