Loans and Allowance for Credit Losses - Summary of Loans Modified as TDRs (Detail) $ in Millions	3 Months Ended	6 Months Ended
Jun. 30, 2016 USD ($) SecurityLoan	Jun. 30, 2015 USD ($) SecurityLoan	Jun. 30, 2016 USD ($) SecurityLoan	Jun. 30, 2015 USD ($) SecurityLoan
Financing Receivable, Modifications [Line Items]
Number of Loans \| SecurityLoan	9,368	10,496	21,739	20,238
Pre-Modification Outstanding Loan Balance	$ 541	$ 544	$ 1,102	$ 921
Post-Modification Outstanding Loan Balance	$ 449	$ 546	$ 1,010	$ 922
Commercial [Member]
Financing Receivable, Modifications [Line Items]
Number of Loans \| SecurityLoan	495	430	1,096	789
Pre-Modification Outstanding Loan Balance	$ 332	$ 93	$ 492	$ 116
Post-Modification Outstanding Loan Balance	$ 237	$ 98	$ 398	$ 121
Commercial Real Estate [Member]
Financing Receivable, Modifications [Line Items]
Number of Loans \| SecurityLoan	20	29	44	54
Pre-Modification Outstanding Loan Balance	$ 10	$ 27	$ 17	$ 40
Post-Modification Outstanding Loan Balance	$ 10	$ 26	$ 17	$ 39
Residential Mortgages [Member]
Financing Receivable, Modifications [Line Items]
Number of Loans \| SecurityLoan	214	1,065	492	1,439
Pre-Modification Outstanding Loan Balance	$ 16	$ 135	$ 48	$ 186
Post-Modification Outstanding Loan Balance	$ 17	$ 134	$ 49	$ 185
Other Retail [Member]
Financing Receivable, Modifications [Line Items]
Number of Loans \| SecurityLoan	467	662	1,076	1,284
Pre-Modification Outstanding Loan Balance	$ 7	$ 12	$ 18	$ 23
Post-Modification Outstanding Loan Balance	$ 8	$ 12	$ 19	$ 23
Credit Card [Member]
Financing Receivable, Modifications [Line Items]
Number of Loans \| SecurityLoan	6,654	6,352	14,642	12,689
Pre-Modification Outstanding Loan Balance	$ 33	$ 32	$ 71	$ 65
Post-Modification Outstanding Loan Balance	$ 32	$ 32	$ 71	$ 65
Total Loans, Excluding GNMA and Covered Loans [Member]
Financing Receivable, Modifications [Line Items]
Number of Loans \| SecurityLoan	7,850	8,538	17,350	16,255
Pre-Modification Outstanding Loan Balance	$ 398	$ 299	$ 646	$ 430
Post-Modification Outstanding Loan Balance	$ 304	$ 302	$ 554	$ 433
Covered Loans [Member]
Financing Receivable, Modifications [Line Items]
Number of Loans \| SecurityLoan	17	8	20	9
Pre-Modification Outstanding Loan Balance	$ 3	$ 3	$ 3	$ 3
Post-Modification Outstanding Loan Balance	$ 3	$ 3	$ 3	$ 3
Government National Mortgage Association [Member]
Financing Receivable, Modifications [Line Items]
Number of Loans \| SecurityLoan	1,501	1,950	4,369	3,974
Pre-Modification Outstanding Loan Balance	$ 140	$ 242	$ 453	$ 488
Post-Modification Outstanding Loan Balance	$ 142	$ 241	$ 453	$ 486

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Number of financing receivables that have been modified by troubled debt restructurings.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 33
-URI http://asc.fasb.org/extlink&oid=49124121&loc=SL6953676-111524

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