Securities with Unrealized Losses (Detail) (USD $) In Millions, unless otherwise specified	6 Months Ended		12 Months Ended
	Jun. 30, 2014		Dec. 31, 2013
Investments, Unrealized Loss Position [Line Items]
Document Period End Date	Jun. 30, 2014
Less than twelve months, Fair Value	$ 921		$ 10,724
Less than twelve months, Unrealized Losses	4		436
Twelve months or longer, Fair Value	7,196		915
Twelve months or longer, Unrealized Losses	227		98
Total, Fair Value	8,117		11,639
Total, Unrealized Losses	231		534
Temporarily Impaired Securities
Investments, Unrealized Loss Position [Line Items]
Less than twelve months, Fair Value	921		10,619
Less than twelve months, Unrealized Losses	4		434
Twelve months or longer, Fair Value	7,150		915
Twelve months or longer, Unrealized Losses	227		98
Total, Fair Value	8,071		11,534
Total, Unrealized Losses	231		532
Temporarily Impaired Securities | US Treasury Securities [Member]
Investments, Unrealized Loss Position [Line Items]
Less than twelve months, Fair Value	99		1,036
Less than twelve months, Unrealized Losses	0	[1]	47
Twelve months or longer, Fair Value	575		0
Twelve months or longer, Unrealized Losses	17		0
Total, Fair Value	674		1,036
Total, Unrealized Losses	17		47
Temporarily Impaired Securities | US Government Agencies Debt Securities
Investments, Unrealized Loss Position [Line Items]
Less than twelve months, Fair Value	3		398
Less than twelve months, Unrealized Losses	0	[1]	29
Twelve months or longer, Fair Value	615		264
Twelve months or longer, Unrealized Losses	32		28
Total, Fair Value	618		662
Total, Unrealized Losses	32		57
Temporarily Impaired Securities | US States and Political Subdivisions Debt Securities [Member]
Investments, Unrealized Loss Position [Line Items]
Less than twelve months, Fair Value			12
Less than twelve months, Unrealized Losses			0
Twelve months or longer, Fair Value			20
Twelve months or longer, Unrealized Losses			2
Total, Fair Value			32
Total, Unrealized Losses			2
Temporarily Impaired Securities | Mortgage-backed Securities, Issued by US Government Sponsored Enterprises
Investments, Unrealized Loss Position [Line Items]
Less than twelve months, Fair Value	819		9,173
Less than twelve months, Unrealized Losses	4		358
Twelve months or longer, Fair Value	5,946		618
Twelve months or longer, Unrealized Losses	178		67
Total, Fair Value	6,765		9,791
Total, Unrealized Losses	182		425
Temporarily Impaired Securities | Asset-backed Securities [Member]
Investments, Unrealized Loss Position [Line Items]
Less than twelve months, Fair Value	0		0
Less than twelve months, Unrealized Losses	0		0
Twelve months or longer, Fair Value	14		13
Twelve months or longer, Unrealized Losses	0	[1]	1
Total, Fair Value	14		13
Total, Unrealized Losses	0	[1]	1
Other Than Temporarily Impaired Securities [Member]
Investments, Unrealized Loss Position [Line Items]
Less than twelve months, Fair Value	0		105	[2]
Less than twelve months, Unrealized Losses	0		2	[2]
Twelve months or longer, Fair Value	46	[2]	0
Twelve months or longer, Unrealized Losses	0	[1]	0
Total, Fair Value	46	[2]	105	[2]
Total, Unrealized Losses	0	[1]	2	[2]
Other Than Temporarily Impaired Securities [Member] | Mortgage-backed Securities, Issued by Private Enterprises [Member]
Investments, Unrealized Loss Position [Line Items]
Less than twelve months, Fair Value	0		105	[2]
Less than twelve months, Unrealized Losses	0		2	[2]
Twelve months or longer, Fair Value	46	[2]	0
Twelve months or longer, Unrealized Losses	0	[1]	0
Total, Fair Value	46	[2]	105	[2]
Total, Unrealized Losses	$ 0	[1]	$ 2	[2]

[1] Securities with unrealized losses less than $0.5 million are shown as zero.

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