Securities with Unrealized Losses (Detail) (USD $) In Millions	Jun. 30, 2011		Dec. 31, 2010
US Treasury Securities | Temporarily Impaired Securities
Investments, Unrealized Loss Position [Line Items]
Less than twelve months, Fair Value	$ 499		$ 2,010
Less than twelve months, Unrealized Losses	8		45
Total, Fair Value	499		2,010
Total, Unrealized Losses	8		45
US Government Agencies Debt Securities | Temporarily Impaired Securities
Investments, Unrealized Loss Position [Line Items]
Less than twelve months, Fair Value	85		1,426
Less than twelve months, Unrealized Losses	1		7
Total, Fair Value	85		1,426
Total, Unrealized Losses	1		7
US States and Political Subdivisions Debt Securities | Temporarily Impaired Securities
Investments, Unrealized Loss Position [Line Items]
Less than twelve months, Fair Value	9		45
Less than twelve months, Unrealized Losses			1
Twelve months or longer, Fair Value	34		35
Twelve months or longer, Unrealized Losses	2		2
Total, Fair Value	43		80
Total, Unrealized Losses	2		3
Mortgage-backed Securities, Issued by US Government Sponsored Enterprises | Temporarily Impaired Securities
Investments, Unrealized Loss Position [Line Items]
Less than twelve months, Fair Value	477		3,497
Less than twelve months, Unrealized Losses	2		28
Total, Fair Value	477		3,497
Total, Unrealized Losses	2		28
Mortgage-backed Securities, Issued by Private Enterprises | Temporarily Impaired Securities
Investments, Unrealized Loss Position [Line Items]
Less than twelve months, Fair Value	4		18
Twelve months or longer, Fair Value	23		17
Twelve months or longer, Unrealized Losses	3		3
Total, Fair Value	27		35
Total, Unrealized Losses	3		3
Collateralized Debt Obligations | Temporarily Impaired Securities
Investments, Unrealized Loss Position [Line Items]
Less than twelve months, Fair Value	162
Total, Fair Value	162
Asset-backed Securities | Temporarily Impaired Securities
Investments, Unrealized Loss Position [Line Items]
Twelve months or longer, Fair Value	13		14
Twelve months or longer, Unrealized Losses	3		4
Total, Fair Value	13		14
Total, Unrealized Losses	3		4
Corporate And Other Debt Securities | Temporarily Impaired Securities
Investments, Unrealized Loss Position [Line Items]
Twelve months or longer, Fair Value	3		3
Twelve months or longer, Unrealized Losses	1		1
Total, Fair Value	3		3
Total, Unrealized Losses	1		1
Temporarily Impaired Securities
Investments, Unrealized Loss Position [Line Items]
Less than twelve months, Fair Value	1,236		6,996
Less than twelve months, Unrealized Losses	11		81
Twelve months or longer, Fair Value	73		69
Twelve months or longer, Unrealized Losses	9		10
Total, Fair Value	1,309		7,065
Total, Unrealized Losses	20		91
Mortgage-backed Securities, Issued by Private Enterprises | Other Than Temporarily Impaired Securities
Investments, Unrealized Loss Position [Line Items]
Less than twelve months, Fair Value	19	[1]
Less than twelve months, Unrealized Losses	1	[1]
Twelve months or longer, Fair Value	241	[1]	286	[1]
Twelve months or longer, Unrealized Losses	21	[1]	31	[1]
Total, Fair Value	260	[1]	286	[1]
Total, Unrealized Losses	22	[1]	31	[1]
Asset-backed Securities | Other Than Temporarily Impaired Securities
Investments, Unrealized Loss Position [Line Items]
Less than twelve months, Fair Value	2	[1]	4	[1]
Less than twelve months, Unrealized Losses			1	[1]
Twelve months or longer, Fair Value	3	[1]
Twelve months or longer, Unrealized Losses	1	[1]
Total, Fair Value	5	[1]	4	[1]
Total, Unrealized Losses	1	[1]	1	[1]
Other Than Temporarily Impaired Securities
Investments, Unrealized Loss Position [Line Items]
Less than twelve months, Fair Value	21	[1]	4	[1]
Less than twelve months, Unrealized Losses	1	[1]	1	[1]
Twelve months or longer, Fair Value	244	[1]	286	[1]
Twelve months or longer, Unrealized Losses	22	[1]	31	[1]
Total, Fair Value	265	[1]	290	[1]
Total, Unrealized Losses	23	[1]	32	[1]
Impaired Securities
Investments, Unrealized Loss Position [Line Items]
Less than twelve months, Fair Value	1,257		7,000
Less than twelve months, Unrealized Losses	12		82
Twelve months or longer, Fair Value	317		355
Twelve months or longer, Unrealized Losses	31		41
Total, Fair Value	1,574		7,355
Total, Unrealized Losses	$ 43		$ 123

[1] Includes OTTI securities for which credit losses have been recorded in earnings in current or prior periods.