Investment Securities - Investment Securities (Detail) (USD $) In Millions, unless otherwise specified	9 Months Ended		12 Months Ended
	Sep. 30, 2014		Dec. 31, 2013
Contractual Maturities of Investment Securities [Line Items]
Available-for-sale securities, total, amortized cost	$ 52,314		$ 41,059
Available-for-sale securities, total, fair value	52,674	[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	2.35%		2.64%
Held-to-maturity securities, total, amortized cost	44,231	[1]	38,920	[1]
Held-to-maturity securities, total, fair value	44,094		38,368
Held-to-maturity securities, total, weighted average maturity in years	4 years 4 months 24 days		4 years 6 months
Held-to-maturity securities, total, weighted average yield	1.93%		2.00%
Amortized Cost of Investment Securities	96,545		79,979
Amortized Cost of Investment Securities, Percentage	100.00%		100.00%
U.S. Treasury and agencies [Member]
Contractual Maturities of Investment Securities [Line Items]
Available-for-sale securities, maturing in one year or less, amortized cost	27
Available-for-sale securities, maturing after one year through five years, amortized cost	1,385
Available-for-sale securities, maturing after five years through ten years, amortized cost	1,179
Available-for-sale securities, maturing after ten years, amortized cost	101
Available-for-sale securities, total, amortized cost	2,692		1,108
Available-for-sale securities, maturing in one year or less, fair value	27
Available-for-sale securities, maturing after one year through five years, fair value	1,387
Available-for-sale securities, maturing after five years through ten years, fair value	1,163
Available-for-sale securities, maturing after ten years, fair value	101
Available-for-sale securities, total, fair value	2,678		1,045
Available-for-sale securities, maturing in one year or less, weighted average maturity in years	3 months 18 days
Available-for-sale securities, maturing after one year through five years, weighted average maturity in years	3 years 8 months 12 days
Available-for-sale securities, maturing after five years through ten years, weighted average maturity in years	8 years 1 month 6 days
Available-for-sale securities, maturing after ten years, weighted average maturity in years	18 years 6 months
Available-for-sale securities, total, weighted average maturity in years	6 years 1 month 6 days
Available-for-sale securities, maturing in one year or less, weighted average yield	4.17%
Available for sale securities, maturing after one year through five years, weighted average yield	1.39%
Available-for-sale securities, maturing after five years through ten years, weighted average yield	2.83%
Available-for-sale securities, maturing after ten years, weighted average yield	1.38%
Available-for-sale securities, total, weighted average yield	2.05%
Held-to-maturity securities, maturing in one year or less, amortized cost	80
Held-to-maturity securities, maturing after one year through five years, amortized cost	1,096
Held-to-maturity securities, maturing after five years through ten years, amortized cost	1,445
Held-to-maturity securities, maturing after ten years, amortized cost	58
Held-to-maturity securities, total, amortized cost	2,679		3,114
Held-to-maturity securities, maturing in one year or less, fair value	81
Held to maturity securities, maturing after one year through five years, fair value	1,096
Held-to-maturity securities, maturing after five years through ten years, fair value	1,412
Held-to-maturity securities, maturing after ten years, fair value	58
Held-to-maturity securities, total, fair value	2,647		3,040
Held-to-maturity securities, maturing in one year or less, weighted average maturity in years	8 months 12 days
Held-to-maturity securities, maturing after one year through five years, weighted average maturity in years	3 years 10 months 24 days
Held-to-maturity securities, maturing after five years through ten years, weighted average maturity in years	7 years 9 months 18 days
Held-to-maturity securities, maturing after ten years, weighted average maturity in years	10 years 9 months 18 days
Held-to-maturity securities, total, weighted average maturity in years	6 years 1 month 6 days
Held-to-maturity securities, maturing in one year or less, weighted average yield	1.36%
Held-to-maturity securities, maturing after one year through five years, weighted average yield	1.42%
Held-to-maturity securities, maturing after five years through ten years, weighted average yield	2.20%
Held-to-maturity securities, maturing after ten years, weighted average yield	1.73%
Held-to-maturity securities, total, weighted average yield	1.85%
Amortized Cost of Investment Securities	5,371		4,222
Amortized Cost of Investment Securities, Percentage	5.50%		5.30%
Mortgage-Backed Securities [Member]
Contractual Maturities of Investment Securities [Line Items]
Available-for-sale securities, maturing in one year or less, amortized cost	565
Available-for-sale securities, maturing after one year through five years, amortized cost	24,490
Available-for-sale securities, maturing after five years through ten years, amortized cost	16,133
Available-for-sale securities, maturing after ten years, amortized cost	1,355
Available-for-sale securities, total, amortized cost	42,543
Available-for-sale securities, maturing in one year or less, fair value	573
Available-for-sale securities, maturing after one year through five years, fair value	24,625
Available-for-sale securities, maturing after five years through ten years, fair value	16,121
Available-for-sale securities, maturing after ten years, fair value	1,350
Available-for-sale securities, total, fair value	42,669
Available-for-sale securities, maturing in one year or less, weighted average maturity in years	8 months 12 days
Available-for-sale securities, maturing after one year through five years, weighted average maturity in years	3 years 9 months 18 days
Available-for-sale securities, maturing after five years through ten years, weighted average maturity in years	5 years 8 months 12 days
Available-for-sale securities, maturing after ten years, weighted average maturity in years	12 years 6 months
Available-for-sale securities, total, weighted average maturity in years	4 years 9 months 18 days
Available-for-sale securities, maturing in one year or less, weighted average yield	1.81%
Available for sale securities, maturing after one year through five years, weighted average yield	2.02%
Available-for-sale securities, maturing after five years through ten years, weighted average yield	1.62%
Available-for-sale securities, maturing after ten years, weighted average yield	1.21%
Available-for-sale securities, total, weighted average yield	1.84%
Held-to-maturity securities, maturing in one year or less, amortized cost	120
Held-to-maturity securities, maturing after one year through five years, amortized cost	28,283
Held-to-maturity securities, maturing after five years through ten years, amortized cost	12,674
Held-to-maturity securities, maturing after ten years, amortized cost	343
Held-to-maturity securities, total, amortized cost	41,420
Held-to-maturity securities, maturing in one year or less, fair value	120
Held to maturity securities, maturing after one year through five years, fair value	28,200
Held-to-maturity securities, maturing after five years through ten years, fair value	12,640
Held-to-maturity securities, maturing after ten years, fair value	346
Held-to-maturity securities, total, fair value	41,306
Held-to-maturity securities, maturing in one year or less, weighted average maturity in years	9 months 18 days
Held-to-maturity securities, maturing after one year through five years, weighted average maturity in years	3 years 7 months 6 days
Held-to-maturity securities, maturing after five years through ten years, weighted average maturity in years	5 years 7 months 6 days
Held-to-maturity securities, maturing after ten years, weighted average maturity in years	12 years 8 months 12 days
Held-to-maturity securities, total, weighted average maturity in years	4 years 3 months 18 days
Held-to-maturity securities, maturing in one year or less, weighted average yield	1.16%
Held-to-maturity securities, maturing after one year through five years, weighted average yield	2.12%
Held-to-maturity securities, maturing after five years through ten years, weighted average yield	1.55%
Held-to-maturity securities, maturing after ten years, weighted average yield	1.17%
Held-to-maturity securities, total, weighted average yield	1.94%
Amortized Cost of Investment Securities	83,963		68,236
Amortized Cost of Investment Securities, Percentage	87.00%		85.30%
Asset-Backed Securities [Member]
Contractual Maturities of Investment Securities [Line Items]
Available-for-sale securities, maturing in one year or less, amortized cost
Available-for-sale securities, maturing after one year through five years, amortized cost	271
Available-for-sale securities, maturing after five years through ten years, amortized cost	357
Available-for-sale securities, maturing after ten years, amortized cost
Available-for-sale securities, total, amortized cost	628
Available-for-sale securities, maturing in one year or less, fair value
Available-for-sale securities, maturing after one year through five years, fair value	281
Available-for-sale securities, maturing after five years through ten years, fair value	364
Available-for-sale securities, maturing after ten years, fair value
Available-for-sale securities, total, fair value	645
Available-for-sale securities, maturing in one year or less, weighted average maturity in years
Available-for-sale securities, maturing after one year through five years, weighted average maturity in years	3 years 6 months
Available-for-sale securities, maturing after five years through ten years, weighted average maturity in years	7 years
Available-for-sale securities, maturing after ten years, weighted average maturity in years
Available-for-sale securities, total, weighted average maturity in years	5 years 6 months
Available-for-sale securities, maturing in one year or less, weighted average yield
Available for sale securities, maturing after one year through five years, weighted average yield	2.32%
Available-for-sale securities, maturing after five years through ten years, weighted average yield	2.15%
Available-for-sale securities, maturing after ten years, weighted average yield
Available-for-sale securities, total, weighted average yield	2.23%
Held-to-maturity securities, maturing in one year or less, amortized cost	1
Held-to-maturity securities, maturing after one year through five years, amortized cost	6
Held-to-maturity securities, maturing after five years through ten years, amortized cost	7
Held-to-maturity securities, maturing after ten years, amortized cost
Held-to-maturity securities, total, amortized cost	14
Held-to-maturity securities, maturing in one year or less, fair value	1
Held to maturity securities, maturing after one year through five years, fair value	9
Held-to-maturity securities, maturing after five years through ten years, fair value	8
Held-to-maturity securities, maturing after ten years, fair value	7
Held-to-maturity securities, total, fair value	25
Held-to-maturity securities, maturing in one year or less, weighted average maturity in years	8 months 12 days
Held-to-maturity securities, maturing after one year through five years, weighted average maturity in years	2 years 10 months 24 days
Held-to-maturity securities, maturing after five years through ten years, weighted average maturity in years	6 years 3 months 18 days
Held-to-maturity securities, maturing after ten years, weighted average maturity in years	15 years 6 months
Held-to-maturity securities, total, weighted average maturity in years	4 years 9 months 18 days
Held-to-maturity securities, maturing in one year or less, weighted average yield	0.78%
Held-to-maturity securities, maturing after one year through five years, weighted average yield	0.89%
Held-to-maturity securities, maturing after five years through ten years, weighted average yield	0.81%
Held-to-maturity securities, maturing after ten years, weighted average yield	0.88%
Held-to-maturity securities, total, weighted average yield	0.84%
Amortized Cost of Investment Securities	642		652
Amortized Cost of Investment Securities, Percentage	0.70%		0.80%
Obligations of state and political subdivisions [Member]
Contractual Maturities of Investment Securities [Line Items]
Available-for-sale securities, maturing in one year or less, amortized cost	724
Available-for-sale securities, maturing after one year through five years, amortized cost	4,121
Available-for-sale securities, maturing after five years through ten years, amortized cost	448
Available-for-sale securities, maturing after ten years, amortized cost	34
Available-for-sale securities, total, amortized cost	5,327		5,673
Available-for-sale securities, maturing in one year or less, fair value	742
Available-for-sale securities, maturing after one year through five years, fair value	4,334
Available-for-sale securities, maturing after five years through ten years, fair value	453
Available-for-sale securities, maturing after ten years, fair value	34
Available-for-sale securities, total, fair value	5,563		5,738
Available-for-sale securities, maturing in one year or less, weighted average maturity in years	7 months 6 days
Available-for-sale securities, maturing after one year through five years, weighted average maturity in years	2 years 3 months 18 days
Available-for-sale securities, maturing after five years through ten years, weighted average maturity in years	6 years 10 months 24 days
Available-for-sale securities, maturing after ten years, weighted average maturity in years	18 years
Available-for-sale securities, total, weighted average maturity in years	2 years 6 months
Available-for-sale securities, maturing in one year or less, weighted average yield	6.66%
Available for sale securities, maturing after one year through five years, weighted average yield	6.79%
Available-for-sale securities, maturing after five years through ten years, weighted average yield	4.76%
Available-for-sale securities, maturing after ten years, weighted average yield	5.06%
Available-for-sale securities, total, weighted average yield	6.59%
Held-to-maturity securities, maturing in one year or less, amortized cost
Held-to-maturity securities, maturing after one year through five years, amortized cost	2
Held-to-maturity securities, maturing after five years through ten years, amortized cost	1
Held-to-maturity securities, maturing after ten years, amortized cost	7
Held-to-maturity securities, total, amortized cost	10		12
Held-to-maturity securities, maturing in one year or less, fair value
Held to maturity securities, maturing after one year through five years, fair value	2
Held-to-maturity securities, maturing after five years through ten years, fair value	1
Held-to-maturity securities, maturing after ten years, fair value	7
Held-to-maturity securities, total, fair value	10		12
Held-to-maturity securities, maturing in one year or less, weighted average maturity in years	4 months 24 days
Held-to-maturity securities, maturing after one year through five years, weighted average maturity in years	2 years 2 months 12 days
Held-to-maturity securities, maturing after five years through ten years, weighted average maturity in years	7 years 4 months 24 days
Held-to-maturity securities, maturing after ten years, weighted average maturity in years	11 years 4 months 24 days
Held-to-maturity securities, total, weighted average maturity in years	9 years
Held-to-maturity securities, maturing in one year or less, weighted average yield	11.64%
Held-to-maturity securities, maturing after one year through five years, weighted average yield	8.31%
Held-to-maturity securities, maturing after five years through ten years, weighted average yield	8.14%
Held-to-maturity securities, maturing after ten years, weighted average yield	2.51%
Held-to-maturity securities, total, weighted average yield	4.54%
Amortized Cost of Investment Securities	5,337		5,685
Amortized Cost of Investment Securities, Percentage	5.50%		7.10%
Other Debt Securities and Obligations of Foreign Governments [Member]
Contractual Maturities of Investment Securities [Line Items]
Available-for-sale securities, maturing in one year or less, amortized cost	6
Available-for-sale securities, maturing after one year through five years, amortized cost
Available-for-sale securities, maturing after five years through ten years, amortized cost
Available-for-sale securities, maturing after ten years, amortized cost	690
Available-for-sale securities, total, amortized cost	696
Available-for-sale securities, maturing in one year or less, fair value	6
Available-for-sale securities, maturing after one year through five years, fair value
Available-for-sale securities, maturing after five years through ten years, fair value
Available-for-sale securities, maturing after ten years, fair value	639
Available-for-sale securities, total, fair value	645
Available-for-sale securities, maturing in one year or less, weighted average maturity in years	4 months 24 days
Available-for-sale securities, maturing after one year through five years, weighted average maturity in years
Available-for-sale securities, maturing after five years through ten years, weighted average maturity in years
Available-for-sale securities, maturing after ten years, weighted average maturity in years	18 years 8 months 12 days
Available-for-sale securities, total, weighted average maturity in years	18 years 7 months 6 days
Available-for-sale securities, maturing in one year or less, weighted average yield	1.01%
Available for sale securities, maturing after one year through five years, weighted average yield
Available-for-sale securities, maturing after five years through ten years, weighted average yield
Available-for-sale securities, maturing after ten years, weighted average yield	2.47%
Available-for-sale securities, total, weighted average yield	2.45%
Held-to-maturity securities, maturing in one year or less, amortized cost	2
Held-to-maturity securities, maturing after one year through five years, amortized cost	82
Held-to-maturity securities, maturing after five years through ten years, amortized cost	24
Held-to-maturity securities, maturing after ten years, amortized cost
Held-to-maturity securities, total, amortized cost	108
Held-to-maturity securities, maturing in one year or less, fair value	2
Held to maturity securities, maturing after one year through five years, fair value	82
Held-to-maturity securities, maturing after five years through ten years, fair value	22
Held-to-maturity securities, maturing after ten years, fair value
Held-to-maturity securities, total, fair value	106
Held-to-maturity securities, maturing in one year or less, weighted average maturity in years
Held-to-maturity securities, maturing after one year through five years, weighted average maturity in years	1 year 2 months 12 days
Held-to-maturity securities, maturing after five years through ten years, weighted average maturity in years	6 years 1 month 6 days
Held-to-maturity securities, maturing after ten years, weighted average maturity in years
Held-to-maturity securities, total, weighted average maturity in years	2 years 2 months 12 days
Held-to-maturity securities, maturing in one year or less, weighted average yield	1.78%
Held-to-maturity securities, maturing after one year through five years, weighted average yield	1.13%
Held-to-maturity securities, maturing after five years through ten years, weighted average yield	0.97%
Held-to-maturity securities, maturing after ten years, weighted average yield
Held-to-maturity securities, total, weighted average yield	1.11%
Amortized Cost of Investment Securities	1,232		1,184
Amortized Cost of Investment Securities, Percentage	1.30%		1.50%
Other Investments Including Perpetual Preferred Securities [Member]
Contractual Maturities of Investment Securities [Line Items]
Available-for-sale securities, total, amortized cost	428
Available-for-sale securities, total, fair value	474
Available-for-sale securities, total, weighted average maturity in years	14 years 4 months 24 days
Available-for-sale securities, total, weighted average yield	2.30%
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.