Loans and Allowance for Credit Losses - Summary of Loans Modified as TDRs (Detail) $ in Millions	3 Months Ended	6 Months Ended
Jun. 30, 2015 USD ($) SecurityLoan	Jun. 30, 2014 USD ($) SecurityLoan	Jun. 30, 2015 USD ($) SecurityLoan	Jun. 30, 2014 USD ($) SecurityLoan
Financing Receivable, Modifications [Line Items]
Number of Loans \| SecurityLoan	10,496	10,791	20,238	22,132
Pre-Modification Outstanding Loan Balance	$ 544	$ 505	$ 921	$ 992
Post-Modification Outstanding Loan Balance	$ 546	$ 495	$ 922	$ 964
Commercial [Member]
Financing Receivable, Modifications [Line Items]
Number of Loans \| SecurityLoan	430	566	789	1,185
Pre-Modification Outstanding Loan Balance	$ 93	$ 74	$ 116	$ 153
Post-Modification Outstanding Loan Balance	$ 98	$ 66	$ 121	$ 143
Commercial Real Estate [Member]
Financing Receivable, Modifications [Line Items]
Number of Loans \| SecurityLoan	29	12	54	27
Pre-Modification Outstanding Loan Balance	$ 27	$ 8	$ 40	$ 19
Post-Modification Outstanding Loan Balance	$ 26	$ 7	$ 39	$ 15
Residential Mortgages [Member]
Financing Receivable, Modifications [Line Items]
Number of Loans \| SecurityLoan	1,065	679	1,439	1,207
Pre-Modification Outstanding Loan Balance	$ 135	$ 91	$ 186	$ 161
Post-Modification Outstanding Loan Balance	$ 134	$ 91	$ 185	$ 161
Credit Card [Member]
Financing Receivable, Modifications [Line Items]
Number of Loans \| SecurityLoan	6,352	6,516	12,689	13,332
Pre-Modification Outstanding Loan Balance	$ 32	$ 36	$ 65	$ 76
Post-Modification Outstanding Loan Balance	$ 32	$ 36	$ 65	$ 76
Other Retail [Member]
Financing Receivable, Modifications [Line Items]
Number of Loans \| SecurityLoan	662	649	1,284	1,436
Pre-Modification Outstanding Loan Balance	$ 12	$ 13	$ 23	$ 34
Post-Modification Outstanding Loan Balance	$ 12	$ 14	$ 23	$ 34
Total Loans, Excluding GNMA and Covered Loans [Member]
Financing Receivable, Modifications [Line Items]
Number of Loans \| SecurityLoan	8,538	8,422	16,255	17,187
Pre-Modification Outstanding Loan Balance	$ 299	$ 222	$ 430	$ 443
Post-Modification Outstanding Loan Balance	$ 302	$ 214	$ 433	$ 429
Loans Purchased from GNMA Mortgage Pools [Member]
Financing Receivable, Modifications [Line Items]
Number of Loans \| SecurityLoan	1,950	2,362	3,974	4,925
Pre-Modification Outstanding Loan Balance	$ 242	$ 281	$ 488	$ 538
Post-Modification Outstanding Loan Balance	$ 241	$ 279	$ 486	$ 525
Covered Loans [Member]
Financing Receivable, Modifications [Line Items]
Number of Loans \| SecurityLoan	8	7	9	20
Pre-Modification Outstanding Loan Balance	$ 3	$ 2	$ 3	$ 11
Post-Modification Outstanding Loan Balance	$ 3	$ 2	$ 3	$ 10

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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=35738203&loc=SL6953676-111524

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