Loans and Allowance for Credit Losses - Summary of Loans Modified as TDRs (Detail) $ in Millions	3 Months Ended
Mar. 31, 2016 USD ($) SecurityLoan	Mar. 31, 2015 USD ($) SecurityLoan
Financing Receivable, Modifications [Line Items]
Number of Loans \| SecurityLoan	12,371	9,742
Pre-Modification Outstanding Loan Balance	$ 561	$ 377
Post-Modification Outstanding Loan Balance	$ 561	$ 376
Commercial [Member]
Financing Receivable, Modifications [Line Items]
Number of Loans \| SecurityLoan	601	359
Pre-Modification Outstanding Loan Balance	$ 160	$ 23
Post-Modification Outstanding Loan Balance	$ 161	$ 23
Commercial Real Estate [Member]
Financing Receivable, Modifications [Line Items]
Number of Loans \| SecurityLoan	24	25
Pre-Modification Outstanding Loan Balance	$ 7	$ 13
Post-Modification Outstanding Loan Balance	$ 7	$ 13
Residential Mortgages [Member]
Financing Receivable, Modifications [Line Items]
Number of Loans \| SecurityLoan	278	374
Pre-Modification Outstanding Loan Balance	$ 32	$ 51
Post-Modification Outstanding Loan Balance	$ 32	$ 51
Other Retail [Member]
Financing Receivable, Modifications [Line Items]
Number of Loans \| SecurityLoan	609	622
Pre-Modification Outstanding Loan Balance	$ 11	$ 11
Post-Modification Outstanding Loan Balance	$ 11	$ 11
Credit Card [Member]
Financing Receivable, Modifications [Line Items]
Number of Loans \| SecurityLoan	7,988	6,337
Pre-Modification Outstanding Loan Balance	$ 38	$ 33
Post-Modification Outstanding Loan Balance	$ 39	$ 33
Total Loans, Excluding GNMA and Covered Loans [Member]
Financing Receivable, Modifications [Line Items]
Number of Loans \| SecurityLoan	9,500	7,717
Pre-Modification Outstanding Loan Balance	$ 248	$ 131
Post-Modification Outstanding Loan Balance	$ 250	$ 131
Covered Loans [Member]
Financing Receivable, Modifications [Line Items]
Number of Loans \| SecurityLoan	3	1
Government National Mortgage Association [Member]
Financing Receivable, Modifications [Line Items]
Number of Loans \| SecurityLoan	2,868	2,024
Pre-Modification Outstanding Loan Balance	$ 313	$ 246
Post-Modification Outstanding Loan Balance	$ 311	$ 245

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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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