Investment Securities - Investment Securities (Detail) (USD $) In Millions, unless otherwise specified	6 Months Ended		12 Months Ended
	Jun. 30, 2014		Dec. 31, 2013
Investment Securities [Line Items]
Available-for-sale securities, total, amortized cost	$ 48,011		$ 41,059
Available-for-sale securities, total, fair value	48,389	[1]	40,935	[1]
Available-for-sale securities, total, weighted average maturity in years	4 years 10 months 24 days		6 years
Available-for-sale securities, total, weighted average yield	2.43%		2.64%
Held-to-maturity securities, total, amortized cost	41,995	[1]	38,920	[1]
Held-to-maturity securities, total, fair value	41,964		38,368
Held-to-maturity securities, total, weighted average maturity in years	4 years 3 months 18 days		4 years 6 months
Held-to-maturity securities, total, weighted average yield	1.98%		2.00%
Total investment securities amortized cost	90,006		79,979
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	1,891		1,108
Available-for-sale securities, total, fair value	1,870		1,045
Available-for-sale securities, total, weighted average maturity in years	6 years 9 months 18 days
Available-for-sale securities, total, weighted average yield	2.17%
Held-to-maturity securities, total, amortized cost	1,982		3,114
Held-to-maturity securities, total, fair value	1,950		3,040
Held-to-maturity securities, total, weighted average maturity in years	6 years 6 months
Held-to-maturity securities, total, weighted average yield	1.86%
Total investment securities amortized cost	3,873		4,222
Total investment securities, percentage	4.30%		5.30%
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	32
Available-for-sale, securities maturing within one year, fair value	32
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	4.36%
Held-to-maturity securities, maturities within one year, amortized cost	180
Held-to-maturity securities, maturities within one year, fair value	181
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	1.15%
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	724
Available-for-sale, securities maturing after one through five year, fair value	728
Available-for-sale securities, total, weighted average maturity in years	3 years 7 months 6 days
Available for sale securities, maturing after one year through five years weighted average yield	1.30%
Held-to-maturity securities, maturities after one year through five years, amortized cost	404
Held to maturity securities, maturities after one year through five years, fair value	406
Held-to-maturity securities, total, weighted average maturity in years	4 years
Held-to-maturity securities, maturing after one year through five years, weighted average yield	1.41%
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	1,034
Available-for-sale, securities maturing after five through ten year, fair value	1,009
Available-for-sale securities, total, weighted average maturity in years	8 years 1 month 6 days
Available-for-sale securities, maturing after five years through ten years, weighted average yield	2.80%
Held-to-maturity securities, maturities after five years through ten years, amortized cost	1,340
Held-to-maturity securities, maturities after five year through ten years, fair value	1,305
Held-to-maturity securities, total, weighted average maturity in years	7 years 9 months 18 days
Held-to-maturity securities, maturing after five year through ten years, weighted average yield	2.09%
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	101
Available-for-sale, securities maturing after ten years, fair value	101
Available-for-sale securities, total, weighted average maturity in years	18 years 9 months 18 days
Available-for-sale securities, maturing after ten years, weighted average yield	1.38%
Held-to-maturity securities, maturities after ten years, amortized cost	58
Held-to-maturity securities, maturities after ten years, fair value	58
Held-to-maturity securities, total, weighted average maturity in years	10 years 10 months 24 days
Held-to-maturity securities, maturing after ten years, weighted average yield	1.73%
Mortgage-Backed Securities [Member]
Investment Securities [Line Items]
Available-for-sale securities, total, amortized cost	38,998
Available-for-sale securities, total, fair value	39,158
Available-for-sale securities, total, weighted average maturity in years	4 years 8 months 12 days
Available-for-sale securities, total, weighted average yield	1.88%
Held-to-maturity securities, total, amortized cost	39,881
Held-to-maturity securities, total, fair value	39,872
Held-to-maturity securities, total, weighted average maturity in years	4 years 2 months 12 days
Held-to-maturity securities, total, weighted average yield	1.99%
Total investment securities amortized cost	78,879		68,236
Total investment securities, percentage	87.60%		85.30%
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	699
Available-for-sale, securities maturing within one year, fair value	705
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	1.84%
Held-to-maturity securities, maturities within one year, amortized cost	134
Held-to-maturity securities, maturities within one year, fair value	133
Held-to-maturity securities, total, weighted average maturity in years	9 months 18 days
Held-to-maturity securities, maturing in one year or less, weighted average yield	1.16%
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	24,383
Available-for-sale, securities maturing after one through five year, fair value	24,569
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	2.04%
Held-to-maturity securities, maturities after one year through five years, amortized cost	28,844
Held to maturity securities, maturities after one year through five years, fair value	28,853
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	2.15%
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	12,680
Available-for-sale, securities maturing after five through ten year, fair value	12,656
Available-for-sale securities, total, weighted average maturity in years	5 years 9 months 18 days
Available-for-sale securities, maturing after five years through ten years, weighted average yield	1.63%
Held-to-maturity securities, maturities after five years through ten years, amortized cost	10,518
Held-to-maturity securities, maturities after five year through ten years, fair value	10,496
Held-to-maturity securities, total, weighted average maturity in years	5 years 6 months
Held-to-maturity securities, maturing after five year through ten years, weighted average yield	1.58%
Mortgage-Backed Securities [Member] | Maturing after ten years [Member]
Investment Securities [Line Items]
Available-for-sale, securities maturing after ten years, amortized cost	1,236
Available-for-sale, securities maturing after ten years, fair value	1,228
Available-for-sale securities, total, weighted average maturity in years	12 years 6 months
Available-for-sale securities, maturing after ten years, weighted average yield	1.21%
Held-to-maturity securities, maturities after ten years, amortized cost	385
Held-to-maturity securities, maturities after ten years, fair value	390
Held-to-maturity securities, total, weighted average maturity in years	12 years 3 months 18 days
Held-to-maturity securities, maturing after ten years, weighted average yield	1.19%
Asset-Backed Securities [Member]
Investment Securities [Line Items]
Available-for-sale securities, total, amortized cost	630
Available-for-sale securities, total, fair value	648
Available-for-sale securities, total, weighted average maturity in years	5 years 9 months 18 days
Available-for-sale securities, total, weighted average yield	1.70%
Held-to-maturity securities, total, amortized cost	14
Held-to-maturity securities, total, fair value	25
Held-to-maturity securities, total, weighted average maturity in years	4 years 9 months 18 days
Held-to-maturity securities, total, weighted average yield	0.83%
Total investment securities amortized cost	644		652
Total investment securities, percentage	0.70%		0.80%
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	0 years
Available-for-sale securities, maturing in one year or less, weighted average yield
Held-to-maturity securities, maturities within one year, amortized cost	2
Held-to-maturity securities, maturities within one year, fair value	2
Held-to-maturity securities, total, weighted average maturity in years	10 months 24 days
Held-to-maturity securities, maturing in one year or less, weighted average yield	0.87%
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	273
Available-for-sale, securities maturing after one through five year, fair value	283
Available-for-sale securities, total, weighted average maturity in years	3 years 8 months 12 days
Available for sale securities, maturing after one year through five years weighted average yield	1.78%
Held-to-maturity securities, maturities after one year through five years, amortized cost	7
Held to maturity securities, maturities after one year through five years, fair value	10
Held-to-maturity securities, total, weighted average maturity in years	3 years 8 months 12 days
Held-to-maturity securities, maturing after one year through five years, weighted average yield	0.83%
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	357
Available-for-sale, securities maturing after five through ten year, fair value	365
Available-for-sale securities, total, weighted average maturity in years	7 years 4 months 24 days
Available-for-sale securities, maturing after five years through ten years, weighted average yield	1.64%
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	6
Held-to-maturity securities, total, weighted average maturity in years	7 years
Held-to-maturity securities, maturing after five year through ten years, weighted average yield	0.84%
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	0 years
Available-for-sale securities, maturing after ten years, weighted average yield
Held-to-maturity securities, maturities after ten years, amortized cost
Held-to-maturity securities, maturities after ten years, fair value	7
Held-to-maturity securities, total, weighted average maturity in years	15 years 9 months 18 days
Held-to-maturity securities, maturing after ten years, weighted average yield	0.48%
Obligations of state and political subdivisions [Member]
Investment Securities [Line Items]
Available-for-sale securities, total, amortized cost	5,362		5,673
Available-for-sale securities, total, fair value	5,598		5,738
Available-for-sale securities, total, weighted average maturity in years	2 years 10 months 24 days
Available-for-sale securities, total, weighted average yield	6.59%
Held-to-maturity securities, total, amortized cost	10		12
Held-to-maturity securities, total, fair value	11		12
Held-to-maturity securities, total, weighted average maturity in years	9 years
Held-to-maturity securities, total, weighted average yield	4.57%
Total investment securities amortized cost	5,372		5,685
Total investment securities, percentage	6.00%		7.10%
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	379
Available-for-sale, securities maturing within one year, fair value	389
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	6.57%
Held-to-maturity securities, maturities within one year, amortized cost	1
Held-to-maturity securities, maturities within one year, fair value	1
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	10.51%
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	4,379
Available-for-sale, securities maturing after one through five year, fair value	4,598
Available-for-sale securities, total, weighted average maturity in years	2 years 3 months 18 days
Available for sale securities, maturing after one year through five years weighted average yield	6.80%
Held-to-maturity securities, maturities after one year through five years, amortized cost	2
Held to maturity securities, maturities after one year through five years, fair value	2
Held-to-maturity securities, total, weighted average maturity in years	2 years 6 months
Held-to-maturity securities, maturing after one year through five years, weighted average yield	8.24%
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	540
Available-for-sale, securities maturing after five through ten year, fair value	549
Available-for-sale securities, total, weighted average maturity in years	6 years 8 months 12 days
Available-for-sale securities, maturing after five years through ten years, weighted average yield	5.07%
Held-to-maturity securities, maturities after five years through ten years, amortized cost	1
Held-to-maturity securities, maturities after five year through ten years, fair value	1
Held-to-maturity securities, total, weighted average maturity in years	7 years 8 months 12 days
Held-to-maturity securities, maturing after five year through ten years, weighted average yield	8.08%
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	64
Available-for-sale, securities maturing after ten years, fair value	62
Available-for-sale securities, total, weighted average maturity in years	22 years 2 months 12 days
Available-for-sale securities, maturing after ten years, weighted average yield	5.52%
Held-to-maturity securities, maturities after ten years, amortized cost	6
Held-to-maturity securities, maturities after ten years, fair value	7
Held-to-maturity securities, total, weighted average maturity in years	11 years 8 months 12 days
Held-to-maturity securities, maturing after ten years, weighted average yield	2.49%
Other Debt Securities and Obligations of Foreign Government [Member]
Investment Securities [Line Items]
Available-for-sale securities, total, amortized cost	696
Available-for-sale securities, total, fair value	635
Available-for-sale securities, total, weighted average maturity in years	18 years 9 months 18 days
Available-for-sale securities, total, weighted average yield	2.45%
Held-to-maturity securities, total, amortized cost	108
Held-to-maturity securities, total, fair value	106
Held-to-maturity securities, total, weighted average maturity in years	3 years 1 month 6 days
Held-to-maturity securities, total, weighted average yield	1.10%
Total investment securities amortized cost	1,238		1,184
Total investment securities, percentage	1.40%		1.50%
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	8 months 12 days
Available-for-sale securities, maturing in one year or less, weighted average yield	1.01%
Held-to-maturity securities, maturities within one year, amortized cost	2
Held-to-maturity securities, maturities within one year, fair value	2
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	1.78%
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	0 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	82
Held to maturity securities, maturities after one year through five years, fair value	82
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	1.13%
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	0 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	24
Held-to-maturity securities, maturities after five year through ten years, fair value	22
Held-to-maturity securities, total, weighted average maturity in years	6 years 3 months 18 days
Held-to-maturity securities, maturing after five year through ten years, weighted average yield	0.96%
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	690
Available-for-sale, securities maturing after ten years, fair value	629
Available-for-sale securities, total, weighted average maturity in years	19 years
Available-for-sale securities, maturing after ten years, weighted average yield	2.46%
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	434
Available-for-sale securities, total, fair value	480
Available-for-sale securities, total, weighted average maturity in years	14 years 7 months 6 days
Available-for-sale securities, total, weighted average yield	2.25%
Held-to-maturity securities, total, 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.