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	Mar. 31, 2021 USD ($) month	Dec. 31, 2020 USD ($) month
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available-for-sale	$ 8,351	$ 8,047
Loans held-for-sale	449	405
Derivative liability	243	125
Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative liability	21	14
Loans net of unearned income	69	77
OREO, fair value	11	15
Loans held for sale | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans held for investment	17	16
Other Assets | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other assets	$ 11	$ 9
Constant prepayment rate | Minimum | Discounted cash flow | Loans held for sale | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans held-for-investment, measurement input	0	0
Constant prepayment rate | Maximum | Discounted cash flow | Loans held for sale | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans held-for-investment, measurement input	0.46	0.26
Constant prepayment rate | Weighted Average | Discounted cash flow | Loans held for sale | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans held-for-investment, measurement input	31	0.11
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	0.57	59
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	0.65	70
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	0.62	0.63
Constant default rate | Minimum | Discounted cash flow | Loans held for sale | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans held-for-investment, measurement input	0	0
Constant default rate | Maximum | Discounted cash flow | Loans held for sale | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans held-for-investment, measurement input	0.15	0.14
Constant default rate | Weighted Average | Discounted cash flow | Loans held for sale | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans held-for-investment, measurement input	1	0.01
Loss severity | Minimum | Discounted cash flow | Loans held for sale | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans held-for-investment, measurement input	0	0
Loss severity | Maximum | Discounted cash flow | Loans held for sale | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans held-for-investment, measurement input	0.93	1
Loss severity | Weighted Average | Discounted cash flow | Loans held for sale | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans held-for-investment, measurement input	7	0.11
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	$ 5,400
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	6,000
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
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	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	50
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
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	12	3
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	36	27
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	26	19
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
Marketability adjustments for specific properties | Minimum | Appraisals from comparable properties | Other Assets | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
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	10
Marketability adjustments for specific properties | Maximum | Appraisals from comparable properties | Other Assets | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other assets, measurement input	0.25	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	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	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	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	10
Adjustments to current sales yields for specific properties | Minimum | Discounted cash flow | Other Assets | 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 | Other Assets | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other assets, measurement input	0.15	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	$ 13
First Mortgages | Prepayment Speeds | 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	0.04	5
First Mortgages | Prepayment Speeds | 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	0.13	15
First Mortgages | Prepayment Speeds | 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	0.05
First Mortgages | Loss severity | 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	0.09	3
First Mortgages | Loss severity | 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	0.17	19
First Mortgages | Loss severity | 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	0.12
Interest- only strips- AFS | Available-for-sale Securities | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available-for-sale	$ 22	$ 32
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 | 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	0.10	0.15
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	0.13	0.17
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	0.11	0.15
SBAs | 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
SBAs | 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	8
SBAs | 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	12
SBAs | 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
SBAs | 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	0.08
SBAs | Bond equivalent yield | 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	7
SBAs | Bond equivalent yield | 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	8
SBAs | 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	0.08	0.07