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
	Mar. 31, 2014	Mar. 31, 2013
Investment income summary:
Interest on fixed maturities	$ 104	$ 102
Dividends on equity securities	32	27
Other investment income	1	1
Total	137	130
Less investment expenses	2	2
Total	135	128
Realized investment gains and losses summary:
Other	2	(3)
Realized gains on investments	22	41
Change in unrealized gains and losses summary:
Unrealized gains (losses) on investments available-for-sale	76	232
Adjustment to deferred acquisition costs and life policy reserves	(3)	3
Amortization of pension actuarial loss and prior service cost	(1)	2
Other	2	(3)
Income taxes on above	41	125
Other comprehensive income (loss), net of tax	74	233
Fixed Maturities
Realized investment gains and losses summary:
Gross realized gains	2	2
Gross realized losses	0	0
Other-than-temporary impairments	0	(2)
Change in unrealized gains and losses summary:
Unrealized gains (losses) on investments available-for-sale	88	(25)
Equity Securities
Realized investment gains and losses summary:
Gross realized gains	18	37
Gross realized losses	0	0
Other-than-temporary impairments	(1)	0
Securities with embedded derivatives	(1)	1
Other	4	3
Change in unrealized gains and losses summary:
Unrealized gains (losses) on investments available-for-sale	29	381
Other	$ 4	$ 3