Pretax Other-Than-Temporary Impairment Losses by Investment Category (Parenthetical) (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2011		Dec. 31, 2010		Dec. 31, 2009
Gain (Loss) on Investments [Line Items]
Other than temporary impairment losses investments portion recognized in earnings net	$ 1,901	[1]	$ 459	[2]	$ 1,361	[2]
Credit Related Impairment
Gain (Loss) on Investments [Line Items]
Other than temporary impairment losses investments portion recognized in earnings net	1,300
Change In Intent Impairment
Gain (Loss) on Investments [Line Items]
Other than temporary impairment losses investments portion recognized in earnings net	$ 615

[1] Includes $1.3 billion for credit-related impairments and $615 million from change in intent to sell securities

[2] Consisted completely of credit-related impairments