Investment Securities (Detail) (USD $) In Millions, unless otherwise specified	9 Months Ended
	Sep. 30, 2012 Y		Dec. 31, 2011
Investment Securities [Line Items]
Held-to-maturity securities, total, weighted average yield	2.06%	[1],[2]
Held-to-maturity securities, total, amortized cost	$ 34,509	[2],[3]	$ 18,877	[3]
Total investment securities amortized cost	73,029		70,233
Total investment securities, percentage	100.00%		100.00%
Held-to-maturity securities, total, weighted average maturity in years	3.1
Available-for-sale securities, total, weighted average yield	3.04%	[1],[2]
Fair Value	35,226	[2],[3]	19,216	[3]
Held-to-maturity securities, total, fair value	35,226		19,216
Available-for-sale securities, total, weighted average maturity in years	4.0	[2]
Available-for-sale securities, total, fair value	39,636	[2]
Available-for-sale securities, total, amortized cost	38,520	[2]
U.S. Treasury and Agencies
Investment Securities [Line Items]
Held-to-maturity securities, maturing in one year or less, weighted average yield	0.61%	[1]
Held-to-maturity securities, maturing after one year through five years, weighted average yield	1.00%	[1]
Held-to-maturity securities, maturing after ten years, weighted average yield	1.96%	[1]
Held-to-maturity securities, total, weighted average yield	1.01%	[1]
Held-to-maturity securities, maturing in one year or less, weighted average maturity years	0.3
Total investment securities amortized cost	3,285		3,605
Held-to-maturity securities, maturing after one year through five years, weighted average maturity in years	1.4
Available-for-sale securities, maturing in one year or less, weighted average yield	2.57%	[1]
Total investment securities, percentage	4.50%		5.10%
Available for sale securities, maturing after one year through five years weighted average yield	0.84%	[1]
Held-to-maturity securities, maturing after ten years, weighted average maturity in years	12.4
Available-for-sale securities, maturing after five years through ten years, weighted average yield	3.11%	[1]
Held-to-maturity securities, total, weighted average maturity in years	1.7
Available-for-sale securities, maturing after ten years, weighted average yield	2.89%	[1]
Held-to-maturity securities, maturities within one year, fair value	50
Available-for-sale securities, total, weighted average yield	1.51%	[1]
Held to maturity securities, maturities after one year through five years, fair value	2,473
Held-to-maturity securities, maturities after ten years, fair value	60
Fair Value	2,583
Held-to-maturity securities, maturities within one year, amortized cost	50
Held-to-maturity securities, maturities after one year through five years, amortized cost	2,447
Held-to-maturity securities, maturities after ten years, amortized cost	60
Held-to-maturity securities, total, amortized cost	2,557
Available-for-sale securities, maturing in one year or less, weighted average maturity in years	0.5
Available-for-sale securities, maturing after one year through five years, weighted average maturity in years	1.3
Available-for-sale securities, maturing after five years through ten years, weighted average maturity in years	7.5
Available-for-sale securities, maturing after ten years, weighted average maturity in years	10.9
Available-for-sale securities, total, weighted average maturity in years	2.6
Available-for-sale, securities maturing within one year, fair value	73
Available-for-sale, securities maturing after one through five year, fair value	501
Available-for-sale, securities maturing after five through ten year, fair value	158
Available-for-sale, securities maturing after ten years, fair value	11
Available-for-sale securities, total, fair value	743
Available-for-sale, securities maturing within one year, amortized cost	72
Available-for-sale, securities maturing after one through five year, amortized cost	497
Available-for-sale, securities maturing after five through ten year, amortized cost	149
Available-for-sale, securities maturing after ten years, amortized cost	10
Available-for-sale securities, total, amortized cost	728
Mortgage-Backed Securities
Investment Securities [Line Items]
Held-to-maturity securities, maturing in one year or less, weighted average yield	1.52%	[1],[4]
Held-to-maturity securities, maturing after one year through five years, weighted average yield	2.17%	[1],[4]
Held-to-maturity securities, maturing after five year through ten years, weighted average yield	1.50%	[1],[4]
Held-to-maturity securities, maturing after ten years, weighted average yield	1.22%	[1],[4]
Held-to-maturity securities, total, weighted average yield	2.14%	[1],[3]
Held-to-maturity securities, maturing in one year or less, weighted average maturity years	0.7	[4]
Total investment securities amortized cost	61,531		57,561
Held-to-maturity securities, maturing after one year through five years, weighted average maturity in years	3.1	[4]
Available-for-sale securities, maturing in one year or less, weighted average yield	1.58%	[1],[4]
Total investment securities, percentage	84.20%		82.00%
Held to maturity securities, maturing after five year through ten years, weighted average maturity in years	7.4	[4]
Available for sale securities, maturing after one year through five years weighted average yield	2.46%	[1],[4]
Held-to-maturity securities, maturing after ten years, weighted average maturity in years	10.4	[4]
Available-for-sale securities, maturing after five years through ten years, weighted average yield	2.26%	[1],[4]
Held-to-maturity securities, total, weighted average maturity in years	3.2	[4]
Available-for-sale securities, maturing after ten years, weighted average yield	1.49%	[1],[4]
Held-to-maturity securities, maturities within one year, fair value	396	[4]
Available-for-sale securities, total, weighted average yield	2.34%	[1],[4]
Held to maturity securities, maturities after one year through five years, fair value	31,260	[4]
Held-to-maturity securities, maturities after five year through ten years, fair value	758	[4]
Held-to-maturity securities, maturities after ten years, fair value	60	[4]
Fair Value	32,474	[4]
Held-to-maturity securities, maturities within one year, amortized cost	395	[4]
Held-to-maturity securities, maturities after one year through five years, amortized cost	30,583	[4]
Held-to-maturity securities, maturities after five years through ten years, amortized cost	740	[4]
Held-to-maturity securities, maturities after ten years, amortized cost	59	[4]
Held-to-maturity securities, total, amortized cost	31,777	[4]
Available-for-sale securities, maturing in one year or less, weighted average maturity in years	0.6	[4]
Available-for-sale securities, maturing after one year through five years, weighted average maturity in years	3.0	[4]
Available-for-sale securities, maturing after five years through ten years, weighted average maturity in years	6.4	[4]
Available-for-sale securities, maturing after ten years, weighted average maturity in years	12.5	[4]
Available-for-sale securities, total, weighted average maturity in years	3.2	[4]
Available-for-sale, securities maturing within one year, fair value	3,315	[4]
Available-for-sale, securities maturing after one through five year, fair value	23,876	[4]
Available-for-sale, securities maturing after five through ten year, fair value	3,045	[4]
Available-for-sale, securities maturing after ten years, fair value	299	[4]
Available-for-sale securities, total, fair value	30,535	[4]
Available-for-sale, securities maturing within one year, amortized cost	3,312	[4]
Available-for-sale, securities maturing after one through five year, amortized cost	23,074	[4]
Available-for-sale, securities maturing after five through ten year, amortized cost	3,074	[4]
Available-for-sale, securities maturing after ten years, amortized cost	294	[4]
Available-for-sale securities, total, amortized cost	29,754	[4]
Asset-Backed Securities
Investment Securities [Line Items]
Held-to-maturity securities, maturing in one year or less, weighted average yield	1.22%	[1],[4]
Held-to-maturity securities, maturing after one year through five years, weighted average yield	0.65%	[1],[4]
Held-to-maturity securities, maturing after five year through ten years, weighted average yield	0.73%	[1],[4]
Held-to-maturity securities, maturing after ten years, weighted average yield	0.86%	[1],[4]
Held-to-maturity securities, total, weighted average yield	0.75%	[1],[4]
Held-to-maturity securities, maturing in one year or less, weighted average maturity years	0.5	[4]
Total investment securities amortized cost	646		949
Held-to-maturity securities, maturing after one year through five years, weighted average maturity in years	3.5	[4]
Available-for-sale securities, maturing in one year or less, weighted average yield	0.24%	[1],[4]
Total investment securities, percentage	0.90%		1.40%
Held to maturity securities, maturing after five year through ten years, weighted average maturity in years	6.6	[4]
Available for sale securities, maturing after one year through five years weighted average yield	6.36%	[1],[4]
Held-to-maturity securities, maturing after ten years, weighted average maturity in years	22.6	[4]
Available-for-sale securities, maturing after five years through ten years, weighted average yield	2.48%	[1],[4]
Held-to-maturity securities, total, weighted average maturity in years	10.5	[4]
Available-for-sale securities, maturing after ten years, weighted average yield	5.88%	[1],[4]
Held-to-maturity securities, maturities within one year, fair value	4	[4]
Available-for-sale securities, total, weighted average yield	2.68%	[1],[4]
Held to maturity securities, maturities after one year through five years, fair value	9	[4]
Held-to-maturity securities, maturities after five year through ten years, fair value	9	[4]
Held-to-maturity securities, maturities after ten years, fair value	18	[4]
Fair Value	40	[4]
Held-to-maturity securities, maturities after one year through five years, amortized cost	11	[4]
Held-to-maturity securities, maturities after five years through ten years, amortized cost	8	[4]
Held-to-maturity securities, maturities after ten years, amortized cost	9	[4]
Held-to-maturity securities, total, amortized cost	28	[4]
Available-for-sale securities, maturing after one year through five years, weighted average maturity in years	3.2	[4]
Available-for-sale securities, maturing after five years through ten years, weighted average maturity in years	7.6	[4]
Available-for-sale securities, maturing after ten years, weighted average maturity in years	18.8	[4]
Available-for-sale securities, total, weighted average maturity in years	7.3	[4]
Available-for-sale, securities maturing within one year, fair value	9	[4]
Available-for-sale, securities maturing after one through five year, fair value	46	[4]
Available-for-sale, securities maturing after five through ten year, fair value	585	[4]
Available-for-sale securities, total, fair value	640	[4]
Available-for-sale, securities maturing within one year, amortized cost	8	[4]
Available-for-sale, securities maturing after one through five year, amortized cost	36	[4]
Available-for-sale, securities maturing after five through ten year, amortized cost	574	[4]
Available-for-sale securities, total, amortized cost	618	[4]
Obligations of state and political subdivisions
Investment Securities [Line Items]
Held-to-maturity securities, maturing in one year or less, weighted average yield	8.16%	[1],[5],[6]
Held-to-maturity securities, maturing after one year through five years, weighted average yield	7.31%	[1],[5],[6]
Held-to-maturity securities, maturing after five year through ten years, weighted average yield	7.79%	[1],[5],[6]
Held-to-maturity securities, maturing after ten years, weighted average yield	5.42%	[1],[5],[6]
Held-to-maturity securities, total, weighted average yield	6.13%	[1],[5],[6]
Held-to-maturity securities, maturing in one year or less, weighted average maturity years	0.7	[5],[6]
Total investment securities amortized cost	6,106		6,417
Held-to-maturity securities, maturing after one year through five years, weighted average maturity in years	3.2	[5],[6]
Available-for-sale securities, maturing in one year or less, weighted average yield	2.65%	[1],[5],[6]
Total investment securities, percentage	8.40%		9.10%
Held to maturity securities, maturing after five year through ten years, weighted average maturity in years	7.9	[5],[6]
Available for sale securities, maturing after one year through five years weighted average yield	6.79%	[1],[5],[6]
Held-to-maturity securities, maturing after ten years, weighted average maturity in years	14.6	[5],[6]
Available-for-sale securities, maturing after five years through ten years, weighted average yield	6.20%	[1],[5],[6]
Held-to-maturity securities, total, weighted average maturity in years	10.9	[5],[6]
Available-for-sale securities, maturing after ten years, weighted average yield	15.83%	[1],[5],[6]
Available-for-sale securities, total, weighted average yield	6.68%	[1],[5],[6]
Held to maturity securities, maturities after one year through five years, fair value	6	[5],[6]
Held-to-maturity securities, maturities after five year through ten years, fair value	2	[5],[6]
Held-to-maturity securities, maturities after ten years, fair value	14	[5],[6]
Fair Value	22	[5],[6]
Held-to-maturity securities, maturities after one year through five years, amortized cost	6	[5],[6]
Held-to-maturity securities, maturities after five years through ten years, amortized cost	1	[5],[6]
Held-to-maturity securities, maturities after ten years, amortized cost	14	[5],[6]
Held-to-maturity securities, total, amortized cost	21	[5],[6]
Available-for-sale securities, maturing in one year or less, weighted average maturity in years	0.1	[5],[6]
Available-for-sale securities, maturing after one year through five years, weighted average maturity in years	3.8	[5],[6]
Available-for-sale securities, maturing after five years through ten years, weighted average maturity in years	7.1	[5],[6]
Available-for-sale securities, maturing after ten years, weighted average maturity in years	17.2	[5],[6]
Available-for-sale securities, total, weighted average maturity in years	4.2	[5],[6]
Available-for-sale, securities maturing within one year, fair value	82	[5],[6]
Available-for-sale, securities maturing after one through five year, fair value	5,550	[5],[6]
Available-for-sale, securities maturing after five through ten year, fair value	812	[5],[6]
Available-for-sale, securities maturing after ten years, fair value	13	[5],[6]
Available-for-sale securities, total, fair value	6,457	[5],[6]
Available-for-sale, securities maturing within one year, amortized cost	81	[5],[6]
Available-for-sale, securities maturing after one through five year, amortized cost	5,226	[5],[6]
Available-for-sale, securities maturing after five through ten year, amortized cost	765	[5],[6]
Available-for-sale, securities maturing after ten years, amortized cost	13	[5],[6]
Available-for-sale securities, total, amortized cost	6,085	[5],[6]
Other debt securities and obligations of foreign government
Investment Securities [Line Items]
Held-to-maturity securities, maturing in one year or less, weighted average yield	1.14%	[1]
Held-to-maturity securities, maturing after one year through five years, weighted average yield	1.30%	[1]
Held-to-maturity securities, maturing after five year through ten years, weighted average yield	1.18%	[1]
Held-to-maturity securities, total, weighted average yield	1.27%	[1]
Held-to-maturity securities, maturing in one year or less, weighted average maturity years	0.5
Total investment securities amortized cost	1,461		1,701
Held-to-maturity securities, maturing after one year through five years, weighted average maturity in years	3.5
Available-for-sale securities, maturing in one year or less, weighted average yield	1.00%	[1]
Total investment securities, percentage	2.00%		2.40%
Held to maturity securities, maturing after five year through ten years, weighted average maturity in years	8.1
Held-to-maturity securities, total, weighted average maturity in years	4.4
Available-for-sale securities, maturing after ten years, weighted average yield	3.21%	[1]
Held-to-maturity securities, maturities within one year, fair value	2
Available-for-sale securities, total, weighted average yield	3.19%	[1]
Held to maturity securities, maturities after one year through five years, fair value	91
Held-to-maturity securities, maturities after five year through ten years, fair value	14
Fair Value	107
Held-to-maturity securities, maturities within one year, amortized cost	3
Held-to-maturity securities, maturities after one year through five years, amortized cost	94
Held-to-maturity securities, maturities after five years through ten years, amortized cost	29
Held-to-maturity securities, total, amortized cost	126
Available-for-sale securities, maturing in one year or less, weighted average maturity in years	0.2
Available-for-sale securities, maturing after ten years, weighted average maturity in years	25.3
Available-for-sale securities, total, weighted average maturity in years	25.1
Available-for-sale, securities maturing within one year, fair value	6
Available-for-sale, securities maturing after ten years, fair value	709
Available-for-sale securities, total, fair value	715
Available-for-sale, securities maturing within one year, amortized cost	6
Available-for-sale, securities maturing after ten years, amortized cost	813
Available-for-sale securities, total, amortized cost	819
Other Investments Including Perpetual Preferred Securities
Investment Securities [Line Items]
Available-for-sale securities, total, weighted average yield	2.97%	[1]
Held-to-maturity securities, total, fair value
Available-for-sale securities, total, weighted average maturity in years	15.8
Available-for-sale securities, total, fair value	546
Available-for-sale securities, total, amortized cost	$ 516

[1] Average yields are presented on a fully-taxable equivalent basis under a tax rate of 35 percent. Yields on available-for-sale and held-to-maturity investment securities are computed based on amortized cost balances, excluding any premiums or discounts recorded related to the transfer of investment securities at fair value from available-for-sale to held-to-maturity.

[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] 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.

[4] Information related to asset and mortgage-backed securities included above is presented based upon weighted-average maturities anticipating future prepayments.

[5] Information related to obligations of state and political subdivisions is presented based upon yield to first optional call date if the security is purchased at a premium, yield to maturity if purchased at par or a discount.

[6] Maturity calculations for obligations of state and political subdivisions are based on the first optional call date for securities with a fair value above par and contractual maturity for securities with a fair value equal to or below par.