Loss And Loss Adjustment Expense Reserves (Schedule Of Loss And Loss Adjustment Expenses Reserves) (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2015		Mar. 31, 2014
Loss And Loss Adjustment Expense Reserves [Line Items]
Changes in unearned premium revenue	$ 83		$ 107
Changes in LAE reserves	6		39
Loss And Lae Reserves [Member]
Loss And Loss Adjustment Expense Reserves [Line Items]
Gross loss and LAE reserve, beginning balance	506
Loss payments for cases with reserves	(11)
Accretion of claim liability discount	2
Changes in discount rates	3
Changes in assumptions	8
Changes in unearned premium revenue	5
Changes in LAE reserves	(7)
Other	(7)	[1]
Gross loss and LAE reserve, ending balance	$ 499

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