Asset Quality - Narrative (Details) $ in Millions	12 Months Ended
Dec. 31, 2018 USD ($) SecurityLoan	Dec. 31, 2017 USD ($) SecurityLoan	Dec. 31, 2016 USD ($) SecurityLoan
Accounts, Notes, Loans and Financing Receivable [Line Items]
Percentage of carrying amount of our commercial nonperforming loans outstanding	75.00%
Percentage of nonperforming loans outstanding face value	80.00%
Percentage of loans held for sale and other nonperforming assets	81.00%
Net reduction to interest income	$ 30	$ 25	$ 26
Commitments outstanding to lend additional funds to borrowers	5	2
Financial receivable, modifications, subsequent default, recorded investment	11
OREO	35	31
Provision (credit) for loan and lease losses	$ 248	$ 237	$ 280
Commercial Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of loans \| SecurityLoan	1	0	0
Consumer Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financial receivable, modifications, subsequent default, recorded investment		$ 4	$ 9
Number of loans \| SecurityLoan	253	147	187
Real Estate - Residential Mortgage [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financial receivable, modifications, subsequent default, recorded investment	$ 113	$ 142
Continuing Operations [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Provision (credit) for loan and lease losses	240	227	$ 267
Continuing Operations [Member] \| Purchase Credit Impaired Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Provision (credit) for loan and lease losses	2	3
Commercial Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Interest income recognized on outstanding balances	13	9	10
Commercial Loans [Member] \| Continuing Operations [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Provision (credit) for loan and lease losses	151	130	179
Consumer Loans [Member] \| Continuing Operations [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Provision (credit) for loan and lease losses	89	97	88
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	(11)	$ 2
Foreclosed Residential Real Estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
OREO	$ 35	$ 26

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 receivables that have been modified by troubled debt restructurings within the previous 12 months and for which there was a payment default.

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Amount of investment related to financing receivables modified by troubled debt restructurings within the previous 12 months, for which there was a 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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