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, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Investment income summary:
Interest on fixed maturities	$ 104	$ 105	$ 309	$ 317
Dividends on equity securities	30	28	87	81
Other investment income	1	1	2	3
Total	135	134	398	401
Less investment expenses	2	2	6	6
Total	133	132	392	395
Realized investment gains and losses summary:
Other	(2)	0	(7)	5
Realized gains on investments	22	10	77	29
Change in unrealized gains and losses summary:
Unrealized gains (losses) on investments available-for-sale	40	164	113	278
Adjustment to deferred acquisition costs and life policy reserves	9	(6)	38	(21)
Amortization of pension actuarial loss and prior service cost	2	2	7	5
Other	(2)	0	(7)	5
Income taxes on above	(25)	(88)	74	147
Other comprehensive income (loss), net of tax	46	161	138	270
Fixed Maturities
Realized investment gains and losses summary:
Gross realized gains	5	14	9	30
Gross realized losses	0	0	0	0
Other-than-temporary impairments	0	0	(2)	0
Change in unrealized gains and losses summary:
Unrealized gains (losses) on investments available-for-sale	(28)	110	(335)	188
Equity Securities
Realized investment gains and losses summary:
Gross realized gains	15	1	64	30
Gross realized losses	0	0	0	(1)
Other-than-temporary impairments	0	(2)	0	(32)
Securities with embedded derivatives	0	(4)	1	1
Other	2	1	5	1
Realized gains on investments	22	10
Change in unrealized gains and losses summary:
Unrealized gains (losses) on investments available-for-sale	90	143	509	240
Other	$ 2	$ 1	$ 5	$ 1