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		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Investment income summary:
Interest on fixed maturities	$ 103	$ 103	$ 207	$ 205
Dividends on equity securities	34	30	66	57
Other investment income	1	0	2	1
Total	138	133	275	263
Less investment expenses	2	2	4	4
Total	136	131	271	259
Realized investment gains and losses summary:
Other	6	(2)	8	(5)
Realized gains on investments	14	14	36	55
Change in unrealized gains and losses summary:
Unrealized gains (losses) on investments available-for-sale	153	(159)	229	73
Adjustment to deferred acquisition costs and life policy reserves	(5)	26	(8)	29
Amortization of pension actuarial loss and prior service cost	0	3	(1)	5
Other	6	(2)	8	(5)
Income taxes on above	(82)	76	123	49
Other comprehensive income (loss), net of tax	154	(141)	228	92
Fixed Maturities
Realized investment gains and losses summary:
Gross realized gains	4	2	6	4
Gross realized losses	0	0	0	0
Other-than-temporary impairments	0	0	0	(2)
Change in unrealized gains and losses summary:
Unrealized gains (losses) on investments available-for-sale	93	(282)	181	(307)
Equity Securities
Realized investment gains and losses summary:
Gross realized gains	16	12	34	49
Gross realized losses	0	0	0	0
Other-than-temporary impairments	0	0	(1)	0
Securities with embedded derivatives	(3)	0	(4)	1
Other	(3)	0	1	3
Realized gains on investments	14	14
Change in unrealized gains and losses summary:
Unrealized gains (losses) on investments available-for-sale	142	38	171	419
Other	$ (3)	$ 0	$ 1	$ 3