Investments - Components of Other-than-Temporary Impairment Losses Recognized in Earnings by Asset Type (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Other than Temporary Impairment, Credit Losses Recognized in Earnings [Line Items]
Net OTTI losses recognized in earnings	$ 10	$ 16	$ 17	$ 50
Corporate and Other Bonds [Member]
Other than Temporary Impairment, Credit Losses Recognized in Earnings [Line Items]
Net OTTI losses recognized in earnings	6	8	9	16
Residential Mortgage-Backed [Member]
Other than Temporary Impairment, Credit Losses Recognized in Earnings [Line Items]
Net OTTI losses recognized in earnings	2	2	4	5
Other Asset-Backed [Member]
Other than Temporary Impairment, Credit Losses Recognized in Earnings [Line Items]
Net OTTI losses recognized in earnings		1	1	2
Total Asset-Backed [Member]
Other than Temporary Impairment, Credit Losses Recognized in Earnings [Line Items]
Net OTTI losses recognized in earnings	2	3	5	7
Total Fixed Maturities Available-for-Sale [Member]
Other than Temporary Impairment, Credit Losses Recognized in Earnings [Line Items]
Net OTTI losses recognized in earnings	8	11	14	23
Common Stock [Member]
Other than Temporary Impairment, Credit Losses Recognized in Earnings [Line Items]
Net OTTI losses recognized in earnings	2	3	3	5
Preferred Stock [Member]
Other than Temporary Impairment, Credit Losses Recognized in Earnings [Line Items]
Net OTTI losses recognized in earnings		2		22
Total Equity Securities Available-for-Sale [Member]
Other than Temporary Impairment, Credit Losses Recognized in Earnings [Line Items]
Net OTTI losses recognized in earnings	$ 2	$ 5	$ 3	$ 27