Invested Assets - Realized Investment Gains and Losses (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Net Investment Income [Line Items]
Other-than-temporary impairment losses	$ (26)		$ (49)	$ (5)
Total fixed maturities	4	$ 22	15	67
Total equity securities	27	43	21	131
Other invested assets	51	45	77	153
Total Realized Investment Gains, Net	82	110	113	351
Fixed Maturities [Member]
Net Investment Income [Line Items]
Gross realized gains	20	27	50	104
Gross realized losses	(5)	(5)	(23)	(33)
Other-than-temporary impairment losses	(11)		(12)	(4)
Equity Securities [Member]
Net Investment Income [Line Items]
Gross realized gains	42	$ 43	58	132
Other-than-temporary impairment losses	$ (15)		$ (37)	$ (1)