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, 2014		Mar. 31, 2013
Loss And Loss Adjustment Expense Reserves [Line Items]
Changes in unearned premium revenue	$ 107		$ 130
Changes in LAE reserves	39		68
Loss And Lae Reserves [Member]
Loss And Loss Adjustment Expense Reserves [Line Items]
Gross loss andLAE reserve, beginning balance	641
Loss payments for cases with reserves	(66)
Accretion of claim liability discount	4
Changes in discount rates	20
Changes in assumptions	20
Changes in unearned premium revenue	0
Changes in LAE reserves	(14)
Other	(3)	[1]
Gross loss andLAE reserve, ending balance	$ 602

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