Loss And Loss Adjustment Expense Reserves (Schedule Of Loss And Loss Adjustment Expenses Reserves) (Detail) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Loss And Loss Adjustment Expense Reserves [Line Items]
Changes in unearned premium revenue		$ 371	$ 412	$ 506
Changes in LAE reserves		(12)	133	216
Loss And Lae Reserves [Member]
Loss And Loss Adjustment Expense Reserves [Line Items]
Gross loss and LAE reserve, beginning balance		506	641
Loss payments for cases with reserves		(200)	(157)
Accretion of claim liability discount		8	14
Changes in discount rates		(41)	79
Changes in assumptions		88	(35)
Changes in unearned premium revenue		14	14
Changes in LAE reserves		4	(19)
Other	[1]	137	(31)
Gross loss and LAE reserve, ending balance		$ 516	$ 506	$ 641

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