Investment Securities Held To Maturities (Detail) (USD $) In Millions, unless otherwise specified	Sep. 30, 2012		Dec. 31, 2011
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	$ 34,509	[1],[2]	$ 18,877	[1]
Unrealized Gains	745	[1]	383	[1]
Unrealized Losses Other-than-Temporary	(4)	[1],[3]	(6)	[1],[3]
Unrealized Losses Other	(24)	[1],[3]	(38)	[1],[4]
Fair Value	35,226	[1],[2]	19,216	[1]
U.S. Treasury and Agencies
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	2,557	[1]	2,560	[1]
Unrealized Gains	26	[1]	35	[1]
Fair Value	2,583	[1]	2,595	[1]
Collateralized debt/loan obligation asset-backed securities
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	9	[1]	52	[1]
Unrealized Gains	16	[1]	13	[1]
Unrealized Losses Other			(2)	[1],[4]
Fair Value	25	[1]	63	[1]
Asset Backed Securities Other
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	19	[1]	23	[1]
Unrealized Gains	2	[1]	1	[1]
Unrealized Losses Other-than-Temporary	(4)	[1],[3]	(6)	[1],[3]
Unrealized Losses Other	(2)	[1],[3]	(1)	[1],[4]
Fair Value	15	[1]	17	[1]
Obligations of state and political subdivisions
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	21	[1]	23	[1]
Unrealized Gains	1	[1]	1	[1]
Unrealized Losses Other			(1)	[1],[4]
Fair Value	22	[1]	23	[1]
Obligations of Foreign Governments
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	7	[1]	7	[1]
Fair Value	7	[1]	7	[1]
Other debt securities
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	119	[1]	121	[1]
Unrealized Losses Other	(19)	[1],[3]	(29)	[1],[4]
Fair Value	100	[1]	92	[1]
Residential Agency | Residential
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	31,773	[1]	16,085	[1]
Unrealized Gains	700	[1]	333	[1]
Unrealized Losses Other	(3)	[1],[3]	(3)	[1],[4]
Fair Value	32,470	[1]	16,415	[1]
Residential non-agency non-prime | Residential
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	1	[1],[5]	2	[1],[5]
Fair Value	1	[1],[5]	2	[1],[5]
Non-agency | Commercial Mortgage-Backed Securities
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	3	[1]	4	[1]
Unrealized Losses Other			(2)	[1],[4]
Fair Value	$ 3	[1]	$ 2	[1]

[1] Held-to-maturity investment securities are carried at historical cost or at fair value at the time of transfer from the available-for-sale to held-to-maturity category, adjusted for amortization of premiums and accretion of discounts and credit-related other-than-temporary impairment.

[2] The weighted-average maturity of the available-for-sale investment securities was 5.2 years at December 31, 2011, with a corresponding weighted-average yield of 3.19 percent. The weighted-average maturity of the held-to-maturity investment securities was 3.9 years at December 31, 2011, with a corresponding weighted-average yield of 2.21 percent.

[3] Represents impairment not related to credit for those investment securities that have been determined to be other-than-temporarily impaired.

[4] Represents unrealized losses on investment securities that have not been determined to be other-than-temporarily impaired.

[5] Includes all securities not meeting the conditions to be designated as prime.