Investments - Components of OTTI Losses Recognized in Earnings by Asset Type (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Other than Temporary Impairment, Credit Losses Recognized in Earnings [Line Items]
Net OTTI losses recognized in earnings	$ 81	$ 156	$ 77
Corporate and Other Bonds [Member]
Other than Temporary Impairment, Credit Losses Recognized in Earnings [Line Items]
Net OTTI losses recognized in earnings	59	104	18
States, Municipalities and Political Subdivisions [Member]
Other than Temporary Impairment, Credit Losses Recognized in Earnings [Line Items]
Net OTTI losses recognized in earnings		18	46
Residential Mortgage-Backed [Member]
Other than Temporary Impairment, Credit Losses Recognized in Earnings [Line Items]
Net OTTI losses recognized in earnings	10	8	5
Other Asset-Backed [Member]
Other than Temporary Impairment, Credit Losses Recognized in Earnings [Line Items]
Net OTTI losses recognized in earnings	3	1	1
Total Asset-Backed [Member]
Other than Temporary Impairment, Credit Losses Recognized in Earnings [Line Items]
Net OTTI losses recognized in earnings	13	9	6
Total Fixed Maturities Available-for-Sale [Member]
Other than Temporary Impairment, Credit Losses Recognized in Earnings [Line Items]
Net OTTI losses recognized in earnings	72	131	70
Common Stock [Member]
Other than Temporary Impairment, Credit Losses Recognized in Earnings [Line Items]
Net OTTI losses recognized in earnings	$ 9	$ 25	$ 7