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Summary of Significant Accounting Policies - Narrative (Details) |  | 12 Months Ended |
--- | --- | --- | ---
Jan. 01, 2020 | Dec. 31, 2019 USD ($) Segment state ATM Branch | Jan. 01, 2019 USD ($)
Accounting Policies [Line Items] |  |  |
Number of retail branches | Branch |  | 1,098 |
Number of automated teller machines | ATM |  | 1,420 |
Number of states with automated teller machines | state |  | 15 |
Number of business groups | Segment |  | 2 |
Number of days to designate the loan as nonaccrual for commercial loan payment due period |  | 90 days |
Number of days to designate commercial loans will be charged off in full or charged down to the fair value of the underlying collateral payment due period |  | 180 days |
Number of days to designate the loan as nonaccrual for consumer payment due period |  | 120 days |
Second lien home equity loan with associated first lien due period |  | 120 days |
Number of days to designate the charge-off policy for most consumer loans taking effect, payment due period |  | 120 days |
Number of days to designate home equity and residential mortgage loans to get charged down to the fair value of the underlying collateral payment due period |  | 180 days |
Number of days to designate charge-off policy for credit card loans and similar unsecured products taking effect, payment due period |  | 180 days |
Threshold period by which amortized cost is greater than fair value to be considered as other-than-temporary |  | 6 months |
Minimum outstanding impaired commercial loans |  | $ 2,500,000 |
Amortization period of stock-based compensation awards |  | 5 years |
Vesting period for compensation cost |  | 4 years |
Operating lease, right-of-use assets |  | $ 654,000,000 |
Operating lease, lease liabilities |  | $ 748,000,000 |
Stock Options [Member] |  |  |
Accounting Policies [Line Items] |  |  |
Options expiration years |  | 10 years |
Stock Options [Member] | One year after the grant date [Member] |  |  |
Accounting Policies [Line Items] |  |  |
Rate at which employee stock options granted to be exercisable |  | 25.00% |
Minimum [Member] | Stock Options [Member] |  |  |
Accounting Policies [Line Items] |  |  |
Vesting period for compensation cost |  | 1 year |
Maximum [Member] |  |  |
Accounting Policies [Line Items] |  |  |
Nonperforming loans, collectively evaluated for impairment |  | $ 2,500,000 |
Maximum [Member] | Stock Options [Member] |  |  |
Accounting Policies [Line Items] |  |  |
Options expiration years |  | 10 years |
Accounting Standards Update 2016-02 [Member] |  |  |
Accounting Policies [Line Items] |  |  |
Operating lease, right-of-use assets |  |  | $ 710,000,000
Operating lease, lease liabilities |  |  | $ 710,000,000
Subsequent Event [Member] | Forecast [Member] | Accounting Standards Update 2016-13 [Member] | Minimum [Member] |  |  |
Accounting Policies [Line Items] |  |  |
Allowance for loan and lease losses, percent increase | 20.00% |  |
Subsequent Event [Member] | Forecast [Member] | Accounting Standards Update 2016-13 [Member] | Maximum [Member] |  |  |
Accounting Policies [Line Items] |  |  |
Allowance for loan and lease losses, percent increase | 25.00% |  |

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- Definition Allowance for commercial loans fair value of underlying collateral payment due period. + References No definition available. + Details
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- Definition Allowance for home equity and residential mortgage loans fair value of underlying collateral payment due period. + References No definition available. + Details
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- Definition Impaired And Other Nonaccrual Commercial Loan Payment Due Period + References No definition available. + Details
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- Definition Number Of Automated Teller Machines + References No definition available. + Details
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- Definition Second Lien Home Equity Loan Including First Lien Default Period + References No definition available. + Details
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