Loans - Consumer, Excluding Credit Card Loan Portfolio, Other Consumer Impaired Loans and Loan Modifications (Details) - Consumer, excluding credit card - Other consumer - USD ($) $ in Millions	3 Months Ended	9 Months Ended
Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017
Financing Receivable, Impaired [Line Items]
With an allowance	$ 227		$ 227		$ 272
Without an allowance	41		41		26
Total impaired loans	268		268		298
Allowance for loan losses related to impaired loans	65		65		73
Unpaid principal balance of impaired loans	372		372		402
Impaired loans on nonaccrual status	244		244		268
Average impaired loans	271	$ 366	281	$ 459
Loans modified in TDRs	90		90		102
TDRs on nonaccrual status	$ 66		$ 66		$ 72

Financing Receivable, Modifications, Recorded Investment, Nonaccrual Status

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- Definition

Impaired Financing Receivable, Recorded Investment, Nonaccrual Status

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No definition available.

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

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- Definition

The amount of the outstanding recorded investment related to financing receivables that have been modified by troubled debt restructurings.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 40
-Section 50
-Paragraph 4
-URI http://asc.fasb.org/extlink&oid=82895541&loc=d3e18845-111554

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- Definition

Average amount of investment of impaired financing receivables with related allowance for credit losses and without a related allowance for credit losses.

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Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
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-Paragraph 15
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Amount of investment of impaired financing receivables with related allowance for credit losses and without a related allowance for credit losses.

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Amount of allowance for credit losses related to recorded investment.

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Amount of unpaid principal balance of impaired financing receivables with related allowance for credit losses and without related allowance for credit losses.

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Amount of investment in impaired financing receivables for which there is no related allowance for credit losses.

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Amount of investment in impaired financing receivables for which there is a related allowance for credit losses.

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