Investment Securities - Investment Securities Held to Maturity (Detail) (USD $) In Millions, unless otherwise specified	Jun. 30, 2013		Dec. 31, 2012
Schedule of Held-to-maturity Securities [Line Items]
Held-to-maturity securities, Amortized Cost	$ 34,668	[1]	$ 34,389	[1]
Held-to-maturity securities, Unrealized Gains	268		590
Held-to-maturity securities, Unrealized Losses Other-than-Temporary	(2)		(3)
Held-to-maturity securities, Unrealized Losses Other	(420)		(24)
Held-to-maturity securities, Fair Value	34,514		34,952
U.S. Treasury and agencies [Member]
Schedule of Held-to-maturity Securities [Line Items]
Held-to-maturity securities, Amortized Cost	3,521		3,154
Held-to-maturity securities, Unrealized Gains	13		27
Held-to-maturity securities, Unrealized Losses Other	(48)
Held-to-maturity securities, Fair Value	3,486		3,181
Collateralized Debt/Loan Obligation Asset-Backed Securities [Member]
Schedule of Held-to-maturity Securities [Line Items]
Held-to-maturity securities, Amortized Cost	3		7
Held-to-maturity securities, Unrealized Gains	11		15
Held-to-maturity securities, Fair Value	14		22
Asset Backed Securities Other [Member]
Schedule of Held-to-maturity Securities [Line Items]
Held-to-maturity securities, Amortized Cost	17		19
Held-to-maturity securities, Unrealized Gains	3		2
Held-to-maturity securities, Unrealized Losses Other-than-Temporary	(2)		(3)
Held-to-maturity securities, Unrealized Losses Other			(1)
Held-to-maturity securities, Fair Value	18		17
Obligations of state and political subdivisions [Member]
Schedule of Held-to-maturity Securities [Line Items]
Held-to-maturity securities, Amortized Cost	17		20
Held-to-maturity securities, Unrealized Gains	1		1
Held-to-maturity securities, Unrealized Losses Other	(1)
Held-to-maturity securities, Fair Value	17		21
Obligations of foreign governments [Member]
Schedule of Held-to-maturity Securities [Line Items]
Held-to-maturity securities, Amortized Cost	7		7
Held-to-maturity securities, Fair Value	7		7
Other debt securities [Member]
Schedule of Held-to-maturity Securities [Line Items]
Held-to-maturity securities, Amortized Cost	114		115
Held-to-maturity securities, Unrealized Losses Other	(13)		(17)
Held-to-maturity securities, Fair Value	101		98
Agency [Member] | Residential [Member]
Schedule of Held-to-maturity Securities [Line Items]
Held-to-maturity securities, Amortized Cost	30,986		31,064
Held-to-maturity securities, Unrealized Gains	240		545
Held-to-maturity securities, Unrealized Losses Other	(358)		(6)
Held-to-maturity securities, Fair Value	30,868		31,603
Residential Non-Agency Non-Prime [Member] | Residential [Member]
Schedule of Held-to-maturity Securities [Line Items]
Held-to-maturity securities, Amortized Cost	1		1
Held-to-maturity securities, Fair Value	1		1
Non-Agency [Member] | Commercial [Member]
Schedule of Held-to-maturity Securities [Line Items]
Held-to-maturity securities, Amortized Cost	2		2
Held-to-maturity securities, Fair Value	$ 2		$ 2

[1] Includes only collateral pledged by the Company where counterparties have the right to sell or pledge the collateral.