Pretax Other-Than-Temporary Impairment Losses by Investment Category (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]
Other-than-temporary impairment losses	$ 528	$ 0	$ 933	$ 42
Perpetual Securities
Gain (Loss) on Investments [Line Items]
Other-than-temporary impairment losses	184	0	184	41
Corporate Bonds
Gain (Loss) on Investments [Line Items]
Other-than-temporary impairment losses	343	0	740	0
Mortgage- and asset-backed Securities
Gain (Loss) on Investments [Line Items]
Other-than-temporary impairment losses	1	0	7	0
Municipalities
Gain (Loss) on Investments [Line Items]
Other-than-temporary impairment losses	0	0	1	0
Equity Securities
Gain (Loss) on Investments [Line Items]
Other-than-temporary impairment losses	$ 0	$ 0	$ 1	$ 1