Invested Assets - Realized Investment Gains and Losses (Detail) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Net Investment Income [Line Items]
Other-than-temporary impairment losses		$ (5)	$ (23)	$ (5)
Total fixed maturities	$ 4	48	11	45
Total equity securities		22	(6)	88
Other invested assets	16	55	26	108
Total Realized Investment Gains, Net	20	125	31	241
Fixed Maturities [Member]
Net Investment Income [Line Items]
Gross realized gains	17	69	30	77
Gross realized losses	$ (13)	(17)	(18)	(28)
Other-than-temporary impairment losses		(4)	(1)	(4)
Equity Securities [Member]
Net Investment Income [Line Items]
Gross realized gains		23	16	89
Other-than-temporary impairment losses		$ (1)	$ (22)	$ (1)