Information Regarding Pretax Realized Gains and Losses From Investments (Detail) (USD $) In Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2011	Jun. 30, 2010	Jun. 30, 2011	Jun. 30, 2010
Gain (Loss) on Investments [Line Items]
Derivative gains (losses)	$ 42	$ (103)	$ 12	$ (86)
Other-than-temporary impairment losses	(528)	0	(933)	(42)
Total realized investment gains (losses)	(668)	(89)	(1,247)	(135)
Debt Securities
Gain (Loss) on Investments [Line Items]
Gross gains from sales	10	0	36	51
Gross losses from sales	(132)	(110)	(319)	(190)
Net gains (losses) from redemptions	(1)	1	6	1
Total realized investment gains (losses)	(467)	(109)	(1,025)	(138)
Debt Securities | Available-for-sale Securities
Gain (Loss) on Investments [Line Items]
Other-than-temporary impairment losses	(344)	0	(748)	0
Perpetual Securities
Gain (Loss) on Investments [Line Items]
Gross gains from sales	48	125	54	133
Gross losses from sales	(107)	0	(109)	0
Other-than-temporary impairment losses	(184)	0	(184)	(41)
Total realized investment gains (losses)	(243)	125	(239)	92
Equity Securities
Gain (Loss) on Investments [Line Items]
Gross losses from sales	0	(2)	0	(2)
Other-than-temporary impairment losses	0	0	(1)	(1)
Total realized investment gains (losses)	0	(2)	(1)	(3)
Other Assets:
Gain (Loss) on Investments [Line Items]
Derivative gains (losses)	(25)	(103)	(55)	(86)
Other	67	0	73	0
Total realized investment gains (losses)	$ 42	$ (103)	$ 18	$ (86)