Investment Securities - Investment Securities (Detail) (USD $) In Millions, unless otherwise specified	Sep. 30, 2013		Dec. 31, 2012
Investment Securities [Line Items]
Available-for-sale securities, total, amortized cost	$ 39,240		$ 39,040
Available-for-sale securities, total, fair value	39,307	[1]	40,139	[1]
Available-for-sale securities, total, weighted average maturity in years	5 years 6 months		4 years 1 month 6 days
Available-for-sale securities, total, weighted average yield	2.70%
Held-to-maturity securities, Amortized Cost	36,904	[1]	34,389	[1]
Held-to-maturity securities, total, fair value	36,632		34,952
Held-to-maturity securities, total, weighted average maturity in years	4 years 2 months 12 days		3 years 3 months 18 days
Held-to-maturity securities, total, weighted average yield	1.97%
Total investment securities amortized cost	76,144		73,429
Total investment securities, percentage	100.00%		100.00%
U.S. Treasury and agencies [Member]
Investment Securities [Line Items]
Available-for-sale securities, total, amortized cost	1,567
Available-for-sale securities, total, fair value	1,521
Available-for-sale securities, total, weighted average maturity in years	5 years 10 months 24 days
Available-for-sale securities, total, weighted average yield	1.69%
Held-to-maturity securities, total, amortized cost	3,368
Held-to-maturity securities, total, fair value	3,317
Held-to-maturity securities, total, weighted average maturity in years	3 years 4 months 24 days
Held-to-maturity securities, total, weighted average yield	1.34%
Total investment securities amortized cost	4,935		4,365
Total investment securities, percentage	6.50%		5.90%
U.S. Treasury and agencies [Member] | Maturing in one year or less [Member]
Investment Securities [Line Items]
Available-for-sale, securities maturing within one year, amortized cost	578
Available-for-sale, securities maturing within one year, fair value	578
Available-for-sale securities, total, weighted average maturity in years	2 months 12 days
Available-for-sale securities, maturing in one year or less, weighted average yield	0.95%
Held-to-maturity securities, maturities within one year, amortized cost	2,112
Held-to-maturity securities, maturities within one year, fair value	2,120
Held-to-maturity securities, total, weighted average maturity in years	4 months 24 days
Held-to-maturity securities, maturing in one year or less, weighted average yield	0.98%
U.S. Treasury and agencies [Member] | Maturing after one year through five years [Member]
Investment Securities [Line Items]
Available-for-sale, securities maturing after one through five year, amortized cost	48
Available-for-sale, securities maturing after one through five year, fair value	51
Available-for-sale securities, total, weighted average maturity in years	3 years 1 month 6 days
Available for sale securities, maturing after one year through five years weighted average yield	3.39%
Held-to-maturity securities, maturities after one year through five years, amortized cost	80
Held to maturity securities, maturities after one year through five years, fair value	81
Held-to-maturity securities, total, weighted average maturity in years	1 year 8 months 12 days
Held-to-maturity securities, maturing after one year through five years, weighted average yield	1.36%
U.S. Treasury and agencies [Member] | Maturing after five years through ten years [Member]
Investment Securities [Line Items]
Available-for-sale, securities maturing after five through ten year, amortized cost	740
Available-for-sale, securities maturing after five through ten year, fair value	703
Available-for-sale securities, total, weighted average maturity in years	8 years 10 months 24 days
Available-for-sale securities, maturing after five years through ten years, weighted average yield	2.11%
Held-to-maturity securities, maturities after five years through ten years, amortized cost	1,116
Held-to-maturity securities, maturities after five year through ten years, fair value	1,056
Held-to-maturity securities, total, weighted average maturity in years	8 years 8 months 12 days
Held-to-maturity securities, maturing after five year through ten years, weighted average yield	1.99%
U.S. Treasury and agencies [Member] | Maturing after ten years [Member]
Investment Securities [Line Items]
Available-for-sale, securities maturing after ten years, amortized cost	201
Available-for-sale, securities maturing after ten years, fair value	189
Available-for-sale securities, total, weighted average maturity in years	12 years 1 month 6 days
Available-for-sale securities, maturing after ten years, weighted average yield	1.84%
Held-to-maturity securities, maturities after ten years, amortized cost	60
Held-to-maturity securities, maturities after ten years, fair value	60
Held-to-maturity securities, total, weighted average maturity in years	11 years 4 months 24 days
Held-to-maturity securities, maturing after ten years, weighted average yield	1.77%
Mortgage-Backed Securities [Member]
Investment Securities [Line Items]
Available-for-sale securities, total, amortized cost	30,121
Available-for-sale securities, total, fair value	30,192
Available-for-sale securities, total, weighted average maturity in years	5 years 1 month 6 days
Available-for-sale securities, total, weighted average yield	2.01%
Held-to-maturity securities, total, amortized cost	33,380
Held-to-maturity securities, total, fair value	33,160
Held-to-maturity securities, total, weighted average maturity in years	4 years 3 months 18 days
Held-to-maturity securities, total, weighted average yield	2.03%
Total investment securities amortized cost	63,501		61,019
Total investment securities, percentage	83.40%		83.10%
Mortgage-Backed Securities [Member] | Maturing in one year or less [Member]
Investment Securities [Line Items]
Available-for-sale, securities maturing within one year, amortized cost	482
Available-for-sale, securities maturing within one year, fair value	486
Available-for-sale securities, total, weighted average maturity in years	8 months 12 days
Available-for-sale securities, maturing in one year or less, weighted average yield	1.98%
Held-to-maturity securities, maturities within one year, amortized cost	23
Held-to-maturity securities, maturities within one year, fair value	23
Held-to-maturity securities, total, weighted average maturity in years	7 months 6 days
Held-to-maturity securities, maturing in one year or less, weighted average yield	2.13%
Mortgage-Backed Securities [Member] | Maturing after one year through five years [Member]
Investment Securities [Line Items]
Available-for-sale, securities maturing after one through five year, amortized cost	16,679
Available-for-sale, securities maturing after one through five year, fair value	16,697
Available-for-sale securities, total, weighted average maturity in years	3 years 9 months 18 days
Available for sale securities, maturing after one year through five years weighted average yield	2.17%
Held-to-maturity securities, maturities after one year through five years, amortized cost	23,127
Held to maturity securities, maturities after one year through five years, fair value	23,060
Held-to-maturity securities, total, weighted average maturity in years	3 years 7 months 6 days
Held-to-maturity securities, maturing after one year through five years, weighted average yield	2.17%
Mortgage-Backed Securities [Member] | Maturing after five years through ten years [Member]
Investment Securities [Line Items]
Available-for-sale, securities maturing after five through ten year, amortized cost	11,086
Available-for-sale, securities maturing after five through ten year, fair value	11,126
Available-for-sale securities, total, weighted average maturity in years	5 years 10 months 24 days
Available-for-sale securities, maturing after five years through ten years, weighted average yield	1.90%
Held-to-maturity securities, maturities after five years through ten years, amortized cost	9,496
Held-to-maturity securities, maturities after five year through ten years, fair value	9,331
Held-to-maturity securities, total, weighted average maturity in years	5 years 7 months 6 days
Held-to-maturity securities, maturing after five year through ten years, weighted average yield	1.75%
Mortgage-Backed Securities [Member] | Maturing after ten years [Member]
Investment Securities [Line Items]
Available-for-sale, securities maturing after ten years, amortized cost	1,874
Available-for-sale, securities maturing after ten years, fair value	1,883
Available-for-sale securities, total, weighted average maturity in years	12 years 9 months 18 days
Available-for-sale securities, maturing after ten years, weighted average yield	1.23%
Held-to-maturity securities, maturities after ten years, amortized cost	734
Held-to-maturity securities, maturities after ten years, fair value	746
Held-to-maturity securities, total, weighted average maturity in years	12 years 2 months 12 days
Held-to-maturity securities, maturing after ten years, weighted average yield	1.27%
Asset-Backed Securities [Member]
Investment Securities [Line Items]
Available-for-sale securities, total, amortized cost	618
Available-for-sale securities, total, fair value	635
Available-for-sale securities, total, weighted average maturity in years	6 years 4 months 24 days
Available-for-sale securities, total, weighted average yield	2.66%
Held-to-maturity securities, total, amortized cost	18
Held-to-maturity securities, total, fair value	29
Held-to-maturity securities, total, weighted average maturity in years	6 years 3 months 18 days
Held-to-maturity securities, total, weighted average yield	0.85%
Total investment securities amortized cost	636		637
Total investment securities, percentage	0.80%		0.90%
Asset-Backed Securities [Member] | Maturing in one year or less [Member]
Investment Securities [Line Items]
Available-for-sale, securities maturing within one year, amortized cost
Available-for-sale, securities maturing within one year, fair value
Available-for-sale securities, total, weighted average maturity in years
Available-for-sale securities, maturing in one year or less, weighted average yield	7.65%
Held-to-maturity securities, maturities within one year, amortized cost
Held-to-maturity securities, maturities within one year, fair value
Held-to-maturity securities, total, weighted average maturity in years	3 months 18 days
Held-to-maturity securities, maturing in one year or less, weighted average yield	0.41%
Asset-Backed Securities [Member] | Maturing after one year through five years [Member]
Investment Securities [Line Items]
Available-for-sale, securities maturing after one through five year, amortized cost	56
Available-for-sale, securities maturing after one through five year, fair value	62
Available-for-sale securities, total, weighted average maturity in years	2 years 8 months 12 days
Available for sale securities, maturing after one year through five years weighted average yield	2.58%
Held-to-maturity securities, maturities after one year through five years, amortized cost	11
Held to maturity securities, maturities after one year through five years, fair value	14
Held-to-maturity securities, total, weighted average maturity in years	3 years 7 months 6 days
Held-to-maturity securities, maturing after one year through five years, weighted average yield	0.85%
Asset-Backed Securities [Member] | Maturing after five years through ten years [Member]
Investment Securities [Line Items]
Available-for-sale, securities maturing after five through ten year, amortized cost	562
Available-for-sale, securities maturing after five through ten year, fair value	573
Available-for-sale securities, total, weighted average maturity in years	6 years 9 months 18 days
Available-for-sale securities, maturing after five years through ten years, weighted average yield	2.66%
Held-to-maturity securities, maturities after five years through ten years, amortized cost	5
Held-to-maturity securities, maturities after five year through ten years, fair value	5
Held-to-maturity securities, total, weighted average maturity in years	6 years 8 months 12 days
Held-to-maturity securities, maturing after five year through ten years, weighted average yield	0.90%
Asset-Backed Securities [Member] | Maturing after ten years [Member]
Investment Securities [Line Items]
Available-for-sale, securities maturing after ten years, amortized cost
Available-for-sale, securities maturing after ten years, fair value
Available-for-sale securities, total, weighted average maturity in years	17 years 9 months 18 days
Available-for-sale securities, maturing after ten years, weighted average yield	5.19%
Held-to-maturity securities, maturities after ten years, amortized cost	2
Held-to-maturity securities, maturities after ten years, fair value	10
Held-to-maturity securities, total, weighted average maturity in years	21 years 3 months 18 days
Held-to-maturity securities, maturing after ten years, weighted average yield	0.77%
Obligations of state and political subdivisions [Member]
Investment Securities [Line Items]
Available-for-sale securities, total, amortized cost	5,732
Available-for-sale securities, total, fair value	5,820
Available-for-sale securities, total, weighted average maturity in years	4 years 3 months 18 days
Available-for-sale securities, total, weighted average yield	6.61%
Held-to-maturity securities, total, amortized cost	17
Held-to-maturity securities, total, fair value	17
Held-to-maturity securities, total, weighted average maturity in years	11 years 2 months 12 days
Held-to-maturity securities, total, weighted average yield	6.24%
Total investment securities amortized cost	5,749		6,079
Total investment securities, percentage	7.60%		8.30%
Obligations of state and political subdivisions [Member] | Maturing in one year or less [Member]
Investment Securities [Line Items]
Available-for-sale, securities maturing within one year, amortized cost	62
Available-for-sale, securities maturing within one year, fair value	63
Available-for-sale securities, total, weighted average maturity in years	6 months
Available-for-sale securities, maturing in one year or less, weighted average yield	6.16%
Held-to-maturity securities, maturities within one year, amortized cost
Held-to-maturity securities, maturities within one year, fair value
Held-to-maturity securities, total, weighted average maturity in years	6 months
Held-to-maturity securities, maturing in one year or less, weighted average yield	7.31%
Obligations of state and political subdivisions [Member] | Maturing after one year through five years [Member]
Investment Securities [Line Items]
Available-for-sale, securities maturing after one through five year, amortized cost	4,810
Available-for-sale, securities maturing after one through five year, fair value	4,930
Available-for-sale securities, total, weighted average maturity in years	2 years 10 months 24 days
Available for sale securities, maturing after one year through five years weighted average yield	6.73%
Held-to-maturity securities, maturities after one year through five years, amortized cost	3
Held to maturity securities, maturities after one year through five years, fair value	3
Held-to-maturity securities, total, weighted average maturity in years	2 years 2 months 12 days
Held-to-maturity securities, maturing after one year through five years, weighted average yield	9.29%
Obligations of state and political subdivisions [Member] | Maturing after five years through ten years [Member]
Investment Securities [Line Items]
Available-for-sale, securities maturing after five through ten year, amortized cost	486
Available-for-sale, securities maturing after five through ten year, fair value	477
Available-for-sale securities, total, weighted average maturity in years	7 years
Available-for-sale securities, maturing after five years through ten years, weighted average yield	5.81%
Held-to-maturity securities, maturities after five years through ten years, amortized cost	2
Held-to-maturity securities, maturities after five year through ten years, fair value	2
Held-to-maturity securities, total, weighted average maturity in years	7 years 4 months 24 days
Held-to-maturity securities, maturing after five year through ten years, weighted average yield	7.74%
Obligations of state and political subdivisions [Member] | Maturing after ten years [Member]
Investment Securities [Line Items]
Available-for-sale, securities maturing after ten years, amortized cost	374
Available-for-sale, securities maturing after ten years, fair value	350
Available-for-sale securities, total, weighted average maturity in years	20 years 2 months 12 days
Available-for-sale securities, maturing after ten years, weighted average yield	6.14%
Held-to-maturity securities, maturities after ten years, amortized cost	12
Held-to-maturity securities, maturities after ten years, fair value	12
Held-to-maturity securities, total, weighted average maturity in years	14 years
Held-to-maturity securities, maturing after ten years, weighted average yield	5.34%
Other Debt Securities and Obligations of Foreign Government [Member]
Investment Securities [Line Items]
Available-for-sale securities, total, amortized cost	740
Available-for-sale securities, total, fair value	648
Available-for-sale securities, total, weighted average maturity in years	21 years 7 months 6 days
Available-for-sale securities, total, weighted average yield	2.71%
Held-to-maturity securities, total, amortized cost	121
Held-to-maturity securities, total, fair value	109
Held-to-maturity securities, total, weighted average maturity in years	3 years 3 months 18 days
Held-to-maturity securities, total, weighted average yield	1.13%
Total investment securities amortized cost	1,323		1,329
Total investment securities, percentage	1.70%		1.80%
Other Debt Securities and Obligations of Foreign Government [Member] | Maturing in one year or less [Member]
Investment Securities [Line Items]
Available-for-sale, securities maturing within one year, amortized cost	6
Available-for-sale, securities maturing within one year, fair value	6
Available-for-sale securities, total, weighted average maturity in years	4 months 24 days
Available-for-sale securities, maturing in one year or less, weighted average yield	1.16%
Held-to-maturity securities, maturities within one year, amortized cost	4
Held-to-maturity securities, maturities within one year, fair value	4
Held-to-maturity securities, total, weighted average maturity in years	7 months 6 days
Held-to-maturity securities, maturing in one year or less, weighted average yield	1.46%
Other Debt Securities and Obligations of Foreign Government [Member] | Maturing after one year through five years [Member]
Investment Securities [Line Items]
Available-for-sale, securities maturing after one through five year, amortized cost
Available-for-sale, securities maturing after one through five year, fair value
Available-for-sale securities, total, weighted average maturity in years
Available for sale securities, maturing after one year through five years weighted average yield
Held-to-maturity securities, maturities after one year through five years, amortized cost	91
Held to maturity securities, maturities after one year through five years, fair value	91
Held-to-maturity securities, total, weighted average maturity in years	2 years 3 months 18 days
Held-to-maturity securities, maturing after one year through five years, weighted average yield	1.15%
Other Debt Securities and Obligations of Foreign Government [Member] | Maturing after five years through ten years [Member]
Investment Securities [Line Items]
Available-for-sale, securities maturing after five through ten year, amortized cost
Available-for-sale, securities maturing after five through ten year, fair value
Available-for-sale securities, total, weighted average maturity in years
Available-for-sale securities, maturing after five years through ten years, weighted average yield
Held-to-maturity securities, maturities after five years through ten years, amortized cost	26
Held-to-maturity securities, maturities after five year through ten years, fair value	14
Held-to-maturity securities, total, weighted average maturity in years	7 years 1 month 6 days
Held-to-maturity securities, maturing after five year through ten years, weighted average yield	1.01%
Other Debt Securities and Obligations of Foreign Government [Member] | Maturing after ten years [Member]
Investment Securities [Line Items]
Available-for-sale, securities maturing after ten years, amortized cost	734
Available-for-sale, securities maturing after ten years, fair value	642
Available-for-sale securities, total, weighted average maturity in years	21 years 9 months 18 days
Available-for-sale securities, maturing after ten years, weighted average yield	2.73%
Held-to-maturity securities, maturities after ten years, amortized cost
Held-to-maturity securities, maturities after ten years, fair value
Held-to-maturity securities, total, weighted average maturity in years
Held-to-maturity securities, maturing after ten years, weighted average yield
Other Investments Including Perpetual Preferred Securities [Member]
Investment Securities [Line Items]
Available-for-sale securities, total, amortized cost	462
Available-for-sale securities, total, fair value	491
Available-for-sale securities, total, weighted average maturity in years	14 years
Available-for-sale securities, total, weighted average yield	2.12%
Held-to-maturity securities, other investments, amortized cost
Held-to-maturity securities, total, fair value
Held-to-maturity securities, total, weighted average maturity in years
Held-to-maturity securities, total, weighted average yield

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