Fair Value of Assets and Liabilities - Schedule Of Unobservable Inputs Utilized In Determining The Fair Value Of Level 3 Recurring And Non-Recurring Measurements (Details) $ in Millions	Dec. 31, 2020 USD ($) month	Dec. 31, 2019 USD ($) month	Dec. 31, 2018 USD ($)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total securities available for sale	$ 8,047	$ 4,445
Loans held-for-sale	405	14
Derivative liabilities, other	125	44
Non Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other assets	9	11	$ 9
Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative liabilities, other	14	23
Loans net of unearned income	77	42
OREO, fair value	15	16
Level 3 | Non Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other assets	9	11	$ 9
Loans Held For Sale - SBA | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans held-for-sale	1	1
Loans held for investment | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans held for investment	16
Other Assets | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other assets	$ 9	$ 11
Constant prepayment rate | Weighted Average | Discounted cash flow | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans held-for-investment, measurement input	0.11
Constant prepayment rate | Weighted Average | Discounted cash flow | Loans Held For Sale - SBA | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans held-for-sale, measurement input	0.10	0.10
Constant prepayment rate | Minimum | Discounted cash flow | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans held-for-investment, measurement input	0
Constant prepayment rate | Minimum | Discounted cash flow | Loans Held For Sale - SBA | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans held-for-sale, measurement input	0.08
Constant prepayment rate | Maximum | Discounted cash flow | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans held-for-investment, measurement input	0.26
Constant prepayment rate | Maximum | Discounted cash flow | Loans Held For Sale - SBA | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans held-for-sale, measurement input	0.12
Bond equivalent yield | Discounted cash flow | Loans Held For Sale - SBA | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans held-for-sale, measurement input		0.09
Bond equivalent yield | Weighted Average | Discounted cash flow | Loans Held For Sale - SBA | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans held-for-sale, measurement input	0.07	0.09
Bond equivalent yield | Minimum | Discounted cash flow | Loans Held For Sale - SBA | Level 3 | Non Recurring | Small Business Administrations
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans held-for-sale, measurement input	0.07
Bond equivalent yield | Maximum | Discounted cash flow | Loans Held For Sale - SBA | Level 3 | Non Recurring | Small Business Administrations
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans held-for-sale, measurement input	0.08
Prepayment speeds - First mortgage | Minimum | Discounted cash flow | Loans Held For Sale - SBA | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans held-for-sale, measurement input		0.08
Prepayment speeds - First mortgage | Maximum | Discounted cash flow | Loans Held For Sale - SBA | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans held-for-sale, measurement input		0.12
Foreclosure losses | Weighted Average | Discounted cash flow | Loans Held For Sale, Residential Real Estate | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans held-for-sale, measurement input	0.63	0.64
Foreclosure losses | Minimum | Discounted cash flow | Loans Held For Sale, Residential Real Estate | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans held-for-sale, measurement input	0.59	0.50
Foreclosure losses | Maximum | Discounted cash flow | Loans Held For Sale, Residential Real Estate | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans held-for-sale, measurement input	0.70	0.66
Loss severity trends - First mortgage | Weighted Average | Discounted cash flow | Loans held for investment | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans held-for-investment, measurement input	0.11
Loss severity trends - First mortgage | Minimum | Discounted cash flow | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans held-for-investment, measurement input	0
Loss severity trends - First mortgage | Maximum | Discounted cash flow | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans held-for-investment, measurement input	1
Constant default rate | Weighted Average | Discounted cash flow | Loans held for investment | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans held-for-investment, measurement input	0.01
Constant default rate | Minimum | Discounted cash flow | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans held-for-investment, measurement input	0
Constant default rate | Maximum | Discounted cash flow | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans held-for-investment, measurement input	0.14
Visa covered litigation resolution amount | Weighted Average | Discounted cash flow | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative liability, measurement input, value	$ 5,800	$ 5,800
Visa covered litigation resolution amount | Minimum | Discounted cash flow | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative liability, measurement input, value	5,400	6,000
Visa covered litigation resolution amount | Maximum | Discounted cash flow | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative liability, measurement input, value	$ 6,000	$ 5,400
Probability of resolution scenarios | Weighted Average | Discounted cash flow | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative liability, measurement input	0.16	0.16
Probability of resolution scenarios | Minimum | Discounted cash flow | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative liability, measurement input	0.10	0.10
Probability of resolution scenarios | Maximum | Discounted cash flow | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative liability, measurement input	0.50	0.50
Time until resolution | Weighted Average | Discounted cash flow | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative liability, measurement input | month	19	29
Time until resolution | Minimum | Discounted cash flow | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative liability, measurement input | month	3	15
Time until resolution | Maximum | Discounted cash flow | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative liability, measurement input | month	27	39
Marketability adjustments for specific properties | Minimum | Appraisals from comparable properties | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans net of unearned income, measurement input	0	0
Other assets, measurement input	0	0
Marketability adjustments for specific properties | Maximum | Appraisals from comparable properties | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans net of unearned income, measurement input	0.10	0.10
Other assets, measurement input	0.25	0.25
Borrowing base certificates adjustment | Minimum | Other collateral valuations | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans net of unearned income, measurement input	0.20	0.20
Borrowing base certificates adjustment | Maximum | Other collateral valuations | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans net of unearned income, measurement input	0.50	0.50
Financial Statements/Auction values adjustment | Minimum | Other collateral valuations | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans net of unearned income, measurement input	0	0
Financial Statements/Auction values adjustment | Maximum | Other collateral valuations | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans net of unearned income, measurement input	0.25	0.25
Adjustment for value changes since appraisal | Minimum | Appraisals from comparable properties | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
OREO measurement input	0	0
Adjustment for value changes since appraisal | Maximum | Appraisals from comparable properties | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
OREO measurement input	0.10	0.10
Adjustments to current sales yields for specific properties | Minimum | Discounted cash flow | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other assets, measurement input	0	0
Adjustments to current sales yields for specific properties | Maximum | Discounted cash flow | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other assets, measurement input	0.15	0.15
Residential Real Estate | Loans Held For Sale, Residential Real Estate | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans held-for-sale	$ 13	$ 15
First Mortgages | Prepayment speeds - First mortgage | Weighted Average | Discounted cash flow | Loans Held For Sale, Residential Real Estate | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans held-for-sale, measurement input	0.05	0.04
First Mortgages | Prepayment speeds - First mortgage | Minimum | Discounted cash flow | Loans Held For Sale, Residential Real Estate | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans held-for-sale, measurement input	0.05	0.03
First Mortgages | Prepayment speeds - First mortgage | Maximum | Discounted cash flow | Loans Held For Sale, Residential Real Estate | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans held-for-sale, measurement input	0.15	0.14
First Mortgages | Loss severity trends - First mortgage | Weighted Average | Discounted cash flow | Loans Held For Sale, Residential Real Estate | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans held-for-sale, measurement input	0.12	0.14
First Mortgages | Loss severity trends - First mortgage | Minimum | Discounted cash flow | Loans Held For Sale, Residential Real Estate | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans held-for-sale, measurement input	0.03	0.03
First Mortgages | Loss severity trends - First mortgage | Maximum | Discounted cash flow | Loans Held For Sale, Residential Real Estate | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans held-for-sale, measurement input	0.19	0.24
HELOC | Prepayment speeds - First mortgage | Weighted Average | Discounted cash flow | Loans Held For Sale, Residential Real Estate | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans held-for-sale, measurement input		0.08
HELOC | Prepayment speeds - First mortgage | Minimum | Discounted cash flow | Loans Held For Sale, Residential Real Estate | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans held-for-sale, measurement input		0
HELOC | Prepayment speeds - First mortgage | Maximum | Discounted cash flow | Loans Held For Sale, Residential Real Estate | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans held-for-sale, measurement input		0.12
HELOC | Loss severity trends - First mortgage | Weighted Average | Discounted cash flow | Loans Held For Sale, Residential Real Estate | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans held-for-sale, measurement input		0.50
HELOC | Loss severity trends - First mortgage | Minimum | Discounted cash flow | Loans Held For Sale, Residential Real Estate | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans held-for-sale, measurement input		0
HELOC | Loss severity trends - First mortgage | Maximum | Discounted cash flow | Loans Held For Sale, Residential Real Estate | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans held-for-sale, measurement input		0.72
Interest-only strips- AFS | Available-for-sale Securities | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total securities available for sale	$ 32	$ 19
Interest-only strips- AFS | Constant prepayment rate | Discounted cash flow | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities, available-for-sale, measurement input	0.12	0.12
Interest-only strips- AFS | Constant prepayment rate | Weighted Average | Discounted cash flow | Available-for-sale Securities | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities, available-for-sale, measurement input	0.12	0.12
Interest-only strips- AFS | Bond equivalent yield | Weighted Average | Discounted cash flow | Available-for-sale Securities | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities, available-for-sale, measurement input	0.15	0.16
Interest-only strips- AFS | Bond equivalent yield | Minimum | Discounted cash flow | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities, available-for-sale, measurement input	0.15	0.16
Interest-only strips- AFS | Bond equivalent yield | Maximum | Discounted cash flow | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities, available-for-sale, measurement input	0.17	0.17