Investments - Realized Investment Gains and Losses and Change in Unrealized Investment Gains and Losses and Other Items (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
Investment income summary:
Interest on fixed maturities	$ 105	$ 104	$ 312	$ 309
Dividends on equity securities	35	30	101	87
Other investment income	0	1	2	2
Gross investment income	140	135	415	398
Less investment expenses	2	2	6	6
Total	138	133	409	392
Realized investment gains and losses summary:
Other	1	(2)	9	(7)
Realized investment gains, net	65	22	101	77
Change in unrealized gains and losses summary:
Unrealized gains (losses) on investments available-for-sale	(78)	40	151	113
Adjustment to deferred acquisition costs and life policy reserves	4	9	(4)	38
Amortization of pension actuarial loss and prior service cost	1	2	0	7
Other	1	(2)	9	(7)
Income taxes on above	40	(25)	83	74
Other comprehensive income (loss), net of tax	(74)	46	154	138
Fixed Maturities
Realized investment gains and losses summary:
Gross realized gains	6	5	12	10
Gross realized losses	0	0	(4)	0
Other-than-temporary impairments	0	0	0	(2)
Change in unrealized gains and losses summary:
Unrealized gains (losses) on investments available-for-sale	(66)	(28)	115	(335)
Equity Securities
Realized investment gains and losses summary:
Gross realized gains	59	15	93	64
Gross realized losses	0	0	0	0
Other-than-temporary impairments	0	0	(1)	0
Other	0	2	1	5
Realized investment gains, net	65	22
Change in unrealized gains and losses summary:
Unrealized gains (losses) on investments available-for-sale	(54)	90	117	509
Other	$ 0	$ 2	$ 1	$ 5