Securities with Unrealized Losses (Detail) - USD ($) $ in Millions		6 Months Ended	12 Months Ended
		Jun. 30, 2015	Dec. 31, 2014
Investments, Unrealized Loss Position [Line Items]
Less than twelve months, Fair Value		$ 11,346	$ 2,586
Less than twelve months, Unrealized Losses		125	8
Twelve months or longer, Fair Value		1,104	5,057
Twelve months or longer, Unrealized Losses		44	79
Total, Fair Value		12,450	7,643
Total, Unrealized Losses		169	87
Temporarily Impaired Securities
Investments, Unrealized Loss Position [Line Items]
Less than twelve months, Fair Value		11,282	2,517
Less than twelve months, Unrealized Losses		125	7
Twelve months or longer, Fair Value		1,104	5,057
Twelve months or longer, Unrealized Losses		44	79
Total, Fair Value		12,386	7,574
Total, Unrealized Losses		169	86
Temporarily Impaired Securities | US Treasury Securities [Member]
Investments, Unrealized Loss Position [Line Items]
Less than twelve months, Fair Value		1,034	150
Less than twelve months, Unrealized Losses		8	1
Twelve months or longer, Fair Value		0	0
Twelve months or longer, Unrealized Losses		0	0
Total, Fair Value		1,034	150
Total, Unrealized Losses		8	1
Temporarily Impaired Securities | US Government Agencies Debt Securities [Member]
Investments, Unrealized Loss Position [Line Items]
Less than twelve months, Fair Value		76	20
Less than twelve months, Unrealized Losses		1	0	[1]
Twelve months or longer, Fair Value		45	132
Twelve months or longer, Unrealized Losses		1	2
Total, Fair Value		121	152
Total, Unrealized Losses		2	2
Temporarily Impaired Securities | Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Investments, Unrealized Loss Position [Line Items]
Less than twelve months, Fair Value		10,172	2,347
Less than twelve months, Unrealized Losses		116	6
Twelve months or longer, Fair Value		1,048	4,911
Twelve months or longer, Unrealized Losses		43	77
Total, Fair Value		11,220	7,258
Total, Unrealized Losses		159	83
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		11	14
Twelve months or longer, Unrealized Losses	[1]	0	0
Total, Fair Value		11	14
Total, Unrealized Losses	[1]	0	0
Other Than Temporarily Impaired Securities [Member]
Investments, Unrealized Loss Position [Line Items]
Less than twelve months, Fair Value	[2]	64	69
Less than twelve months, Unrealized Losses	[2]	0	1
Twelve months or longer, Fair Value		0	0
Twelve months or longer, Unrealized Losses		0	0
Total, Fair Value	[2]	64	69
Total, Unrealized Losses	[2]	0	1
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	[2]	64	69
Less than twelve months, Unrealized Losses	[2]	0	1
Twelve months or longer, Fair Value		0	0
Twelve months or longer, Unrealized Losses		0	0
Total, Fair Value	[2]	64	69
Total, Unrealized Losses	[2]	$ 0	$ 1

[1] Unrealized losses less than $0.5 million are shown as zero.

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