Asset Quality - Narrative (Details) $ in Millions	12 Months Ended
Dec. 31, 2019 USD ($) SecurityLoan	Dec. 31, 2018 USD ($) SecurityLoan	Dec. 31, 2017 USD ($) SecurityLoan
Accounts, Notes, Loans and Financing Receivable [Line Items]
Percentage of carrying amount of our commercial nonperforming loans outstanding	76.00%
Percentage of nonperforming loans outstanding face value	80.00%
Percentage of loans held for sale and other nonperforming assets	88.00%
Net reduction to interest income	$ 31	$ 30	$ 25
Interest income recognized on outstanding balances	14	13
Commitments outstanding to lend additional funds to borrowers	4	5
Financial receivable, modifications, subsequent default, recorded investment	8	11
OREO	35	35
Provision (credit) for loan and lease losses	$ 444	$ 248	$ 237
Commercial Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of loans \| SecurityLoan	0	1	0
Consumer Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financial receivable, modifications, subsequent default, recorded investment			$ 4
Number of loans \| SecurityLoan	356	253	147
Real Estate - Residential Mortgage [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financial receivable, modifications, subsequent default, recorded investment	$ 97	$ 113
Continuing Operations [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Provision (credit) for loan and lease losses	441	240	$ 227
Commercial Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Interest income recognized on outstanding balances			9
Commercial Loans [Member] \| Continuing Operations [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Provision (credit) for loan and lease losses	332	151	130
Consumer Loans [Member] \| Continuing Operations [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Provision (credit) for loan and lease losses	109	89	97
Consumer Loans [Member] \| Continuing Operations [Member] \| Real Estate - Residential Mortgage [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Provision (credit) for loan and lease losses	1	1	$ (11)
Foreclosed Residential Real Estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
OREO	$ 34	$ 35

Net reduction to interest income.

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Other real estate owned non-performing loan.

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Percentage of carrying amount of our commercial nonperforming loans outstanding.

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Percentage of loans held for sale and other nonperforming assets.

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Percentage of nonperforming loans outstanding face value.

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Significant commitments to lend additional funds to borrowers with loans on nonperforming status.

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Number of financing receivable contracts modified as troubled debt restructuring within previous 12 months, with subsequent payment default.

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Amount of financing receivable modified as troubled debt restructuring within previous 12 months, with subsequent payment default.

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Amount of interest income recognized that the financing receivables (with related allowance for credit losses and without a related allowance for credit losses) were impaired.

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Amount of expense related to estimated loss from loan and lease transactions.

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