Investment Securities - Investment Securities Held-to-Maturity (Detail) - USD ($) $ in Millions		Sep. 30, 2015	Dec. 31, 2014
Schedule of Held-to-maturity Securities [Line Items]
Held-to-maturity securities, Amortized Cost	[1]	$ 44,690	$ 44,974
Held-to-maturity securities, Unrealized Gains		455	362
Held-to-maturity securities, Unrealized Losses Other-than-Temporary		(1)
Held-to-maturity securities, Unrealized Losses Other		(93)	(196)
Held-to-maturity securities, fair value		45,051	45,140
U.S. Treasury and Agencies [Member]
Schedule of Held-to-maturity Securities [Line Items]
Held-to-maturity securities, Amortized Cost		2,937	2,717
Held-to-maturity securities, Unrealized Gains		40	15
Held-to-maturity securities, Unrealized Losses Other		(2)	(18)
Held-to-maturity securities, fair value		2,975	2,714
Mortgage-Backed Securities Residential [Member] | Agency [Member]
Schedule of Held-to-maturity Securities [Line Items]
Held-to-maturity securities, Amortized Cost		41,704	42,204
Held-to-maturity securities, Unrealized Gains		403	335
Held-to-maturity securities, Unrealized Losses Other		(88)	(176)
Held-to-maturity securities, fair value		42,019	42,363
Mortgage-Backed Securities Residential [Member] | Non-Agency Non-Prime [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
Asset-Backed Securities [Member]
Schedule of Held-to-maturity Securities [Line Items]
Held-to-maturity securities, Amortized Cost		10
Held-to-maturity securities, fair value		20
Asset-Backed Securities [Member] | Collateralized Loan Obligations [Member]
Schedule of Held-to-maturity Securities [Line Items]
Held-to-maturity securities, Unrealized Gains		7	7
Held-to-maturity securities, fair value		7	7
Asset-Backed Securities [Member] | Asset-Backed Securities Other [Member]
Schedule of Held-to-maturity Securities [Line Items]
Held-to-maturity securities, Amortized Cost		10	13
Held-to-maturity securities, Unrealized Gains		4	4
Held-to-maturity securities, Unrealized Losses Other-than-Temporary		(1)
Held-to-maturity securities, fair value		13	17
Obligations of State and Political Subdivisions [Member]
Schedule of Held-to-maturity Securities [Line Items]
Held-to-maturity securities, Amortized Cost		8	9
Held-to-maturity securities, Unrealized Gains		1	1
Held-to-maturity securities, Unrealized Losses Other		(1)	(1)
Held-to-maturity securities, fair value		8	9
Obligations of Foreign Governments [Member]
Schedule of Held-to-maturity Securities [Line Items]
Held-to-maturity securities, Amortized Cost		9	9
Held-to-maturity securities, fair value		9	9
Other Debt Securities [Member]
Schedule of Held-to-maturity Securities [Line Items]
Held-to-maturity securities, Amortized Cost		21	21
Held-to-maturity securities, Unrealized Losses Other		(2)	(1)
Held-to-maturity securities, fair value		$ 19	$ 20

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