Loans - Consumer Banking: Risk Profile by Geographic Region, Delinquency Status and Performing Status (Detail) - USD ($) $ in Millions	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment	$ 229,851	$ 208,316	$ 197,199
Past due	6,895	6,070
Nonperforming Loans	$ 1,170	$ 809
Financing Receivable, Nonaccrual, Percent Past Due	0.51%	0.39%
30 Plus day delinquencies (as percent)	3.00%	2.91%
Consumer Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment	$ 70,372	$ 71,439
Percentage of portfolio	100.00%	100.00%
Past due	$ 3,284	$ 3,024
Nonperforming Loans	$ 558	$ 549
Financing Receivable, Nonaccrual, Percent Past Due	0.79%	0.77%
Nonperforming loans, excluding acquired loans (as percent)	1.08%	1.14%
Consumer Portfolio Segment [Member] | Auto
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment	$ 41,549	$ 37,824
Past due	3,000	2,682
Nonperforming Loans	$ 219	$ 197
Financing Receivable, Nonaccrual, Percent Past Due	0.53%	0.52%
Consumer Portfolio Segment [Member] | Auto | Geographic Concentration Risk | Loans Receivable
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment	$ 41,549	$ 37,824
Percentage of portfolio	59.00%	53.00%
Consumer Portfolio Segment [Member] | Auto | Geographic Concentration Risk | Loans Receivable | Texas
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment	$ 5,463	$ 5,248
Percentage of portfolio	7.80%	7.40%
Consumer Portfolio Segment [Member] | Auto | Geographic Concentration Risk | Loans Receivable | California
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment	$ 4,611	$ 4,081
Percentage of portfolio	6.50%	5.70%
Consumer Portfolio Segment [Member] | Auto | Geographic Concentration Risk | Loans Receivable | Louisiana
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment	$ 1,882	$ 1,773
Percentage of portfolio	2.70%	2.50%
Consumer Portfolio Segment [Member] | Auto | Geographic Concentration Risk | Loans Receivable | Illinois
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment	$ 1,859	$ 1,676
Percentage of portfolio	2.60%	2.40%
Consumer Portfolio Segment [Member] | Auto | Geographic Concentration Risk | Loans Receivable | Florida
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment	$ 3,315	$ 2,737
Percentage of portfolio	4.70%	3.80%
Consumer Portfolio Segment [Member] | Auto | Geographic Concentration Risk | Loans Receivable | Georgia
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment	$ 2,245	$ 2,066
Percentage of portfolio	3.20%	2.90%
Consumer Portfolio Segment [Member] | Auto | Geographic Concentration Risk | Loans Receivable | Ohio
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment	$ 1,738	$ 1,566
Percentage of portfolio	2.50%	2.20%
Consumer Portfolio Segment [Member] | Auto | Geographic Concentration Risk | Loans Receivable | Other
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment	$ 20,436	$ 18,677
Percentage of portfolio	29.00%	26.10%
Consumer Portfolio Segment [Member] | Home loan
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment	$ 25,227	$ 30,035
Past due	235	302
Nonperforming Loans	$ 311	$ 330
Financing Receivable, Nonaccrual, Percent Past Due	1.23%	1.10%
Nonperforming loans, excluding acquired loans (as percent)	4.68%	4.86%
Consumer Portfolio Segment [Member] | Home loan | Geographic Concentration Risk | Loans Receivable
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment	$ 25,227	$ 30,035
Percentage of portfolio	35.90%	42.00%
Consumer Portfolio Segment [Member] | Home loan | Geographic Concentration Risk | Loans Receivable | California
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment	$ 5,884	$ 6,943
Percentage of portfolio	8.40%	9.70%
Consumer Portfolio Segment [Member] | Home loan | Geographic Concentration Risk | Loans Receivable | New York
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment	$ 2,171	$ 2,452
Percentage of portfolio	3.10%	3.40%
Consumer Portfolio Segment [Member] | Home loan | Geographic Concentration Risk | Loans Receivable | Illinois
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment	$ 1,490	$ 1,873
Percentage of portfolio	2.10%	2.60%
Consumer Portfolio Segment [Member] | Home loan | Geographic Concentration Risk | Loans Receivable | Maryland
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment	$ 1,539	$ 1,720
Percentage of portfolio	2.20%	2.40%
Consumer Portfolio Segment [Member] | Home loan | Geographic Concentration Risk | Loans Receivable | New Jersey
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment	$ 1,293	$ 1,529
Percentage of portfolio	1.80%	2.10%
Consumer Portfolio Segment [Member] | Home loan | Geographic Concentration Risk | Loans Receivable | Virginia
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment	$ 1,354	$ 1,538
Percentage of portfolio	1.90%	2.20%
Consumer Portfolio Segment [Member] | Home loan | Geographic Concentration Risk | Loans Receivable | Florida
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment	$ 1,146	$ 1,375
Percentage of portfolio	1.60%	1.90%
Consumer Portfolio Segment [Member] | Home loan | Geographic Concentration Risk | Loans Receivable | Other
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment	$ 10,350	$ 12,605
Percentage of portfolio	14.80%	17.70%
Consumer Portfolio Segment [Member] | Retail banking
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment	$ 3,596	$ 3,580
Past due	49	40
Nonperforming Loans	$ 28	$ 22
Financing Receivable, Nonaccrual, Percent Past Due	0.77%	0.61%
Consumer Portfolio Segment [Member] | Retail banking | Geographic Concentration Risk | Loans Receivable
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment	$ 3,596	$ 3,580
Percentage of portfolio	5.10%	5.00%
Consumer Portfolio Segment [Member] | Retail banking | Geographic Concentration Risk | Loans Receivable | Texas
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment	$ 757	$ 756
Percentage of portfolio	1.10%	1.10%
Consumer Portfolio Segment [Member] | Retail banking | Geographic Concentration Risk | Loans Receivable | Louisiana
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment	$ 1,071	$ 1,120
Percentage of portfolio	1.50%	1.50%
Consumer Portfolio Segment [Member] | Retail banking | Geographic Concentration Risk | Loans Receivable | New York
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment	$ 921	$ 881
Percentage of portfolio	1.30%	1.20%
Consumer Portfolio Segment [Member] | Retail banking | Geographic Concentration Risk | Loans Receivable | Maryland
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment	$ 180	$ 167
Percentage of portfolio	0.30%	0.20%
Consumer Portfolio Segment [Member] | Retail banking | Geographic Concentration Risk | Loans Receivable | New Jersey
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment	$ 259	$ 265
Percentage of portfolio	0.40%	0.40%
Consumer Portfolio Segment [Member] | Retail banking | Geographic Concentration Risk | Loans Receivable | Virginia
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment	$ 151	$ 132
Percentage of portfolio	0.20%	0.20%
Consumer Portfolio Segment [Member] | Retail banking | Geographic Concentration Risk | Loans Receivable | Other
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment	$ 257	$ 259
Percentage of portfolio	0.30%	0.40%
Financing Receivables, Equal to Greater than 90 Days Past Due [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past due	$ 2,158	$ 1,805
30 Plus day delinquencies (as percent)	0.94%	0.87%
Financing Receivables, Equal to Greater than 90 Days Past Due [Member] | Consumer Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past due	$ 415	$ 431
Financing Receivables, Equal to Greater than 90 Days Past Due [Member] | Consumer Portfolio Segment [Member] | Auto
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past due	219	197
Financing Receivables, Equal to Greater than 90 Days Past Due [Member] | Consumer Portfolio Segment [Member] | Home loan
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past due	176	218
Financing Receivables, Equal to Greater than 90 Days Past Due [Member] | Consumer Portfolio Segment [Member] | Retail banking
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past due	$ 20	$ 16