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Loans - Narrative (Details) - USD ($) | 6 Months Ended | 12 Months Ended |  |  |  |
--- | --- | --- | --- | --- | --- | ---
Jun. 30, 2020 | Dec. 31, 2019 | Mar. 31, 2020 | Jun. 30, 2019 | Mar. 31, 2019 | Dec. 31, 2018
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |  |  |  |
Loans, net of unearned income | $ 32,708,937,000 | [1] | $ 31,061,111,000 | [1] |  | $ 29,712,810,000 |  |
Troubled debt restructurings loans | 192,600,000 |  | 206,300,000 |  |  |  |  |
Allowance for loan losses | $ 537,881,000 |  | 200,307,000 |  | $ 444,490,000 | 192,749,000 | $ 184,911,000 | $ 180,424,000
Loans to Mortgage Companies |  |  |  |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |  |  |  |
Percentage of loans collateralized with government guaranteed loans | 95.00% |  |  |  |  |  |  |
Allowance For TDRs To Recorded Investment Of TDRs |  |  |  |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |  |  |  |
Allowance for loan losses | $ 13,600,000 |  | $ 19,700,000 |  |  |  |  |
Ratio of the allowance for loan losses to loans | 7.00% |  | 10.00% |  |  |  |  |
Loans Held For Sale, Residential Real Estate |  |  |  |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |  |  |  |
Troubled debt restructurings loans | $ 45,100,000 |  | $ 51,100,000 |  |  |  |  |
Commercial |  |  |  |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |  |  |  |
Allowance for loan losses |  |  | 158,598,000 |  |  |  |  |
Allowance - purchased credit-impaired loans |  |  | 848,000 |  |  |  |  |
Commercial | Loans to Mortgage Companies |  |  |  |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |  |  |  |
Financing receivable, before allowance for credit loss | $ 4,000,000,000.0 |  |  |  |  |  |  |
Percentage of commercial & industrial loan portfolio | 19.00% |  |  |  |  |  |  |
Percentage contributed in total loan | 12.00% |  |  |  |  |  |  |
Commercial | Finance Insurance And Loans To Mortgage Companies |  |  |  |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |  |  |  |
Percentage of commercial & industrial loan portfolio | 31.00% |  |  |  |  |  |  |
Commercial | Commercial, financial, and industrial |  |  |  |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |  |  |  |
Loans, net of unearned income | $ 21,393,893,000 |  | 20,051,091,000 |  |  | 19,054,269,000 |  |
Allowance for loan losses | 318,722,000 |  | 122,486,000 |  | 254,516,000 | 116,096,000 | 103,713,000 | 98,947,000
Commercial | Finance And Insurance Companies |  |  |  |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |  |  |  |
Financing receivable, before allowance for credit loss | $ 2,500,000,000 |  |  |  |  |  |  |
Percentage of commercial & industrial loan portfolio | 12.00% |  |  |  |  |  |  |
Percentage contributed in total loan | 8.00% |  |  |  |  |  |  |
Consumer | Consumer Real Estate (a) |  |  |  |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |  |  |  |
Loans, net of unearned income | $ 6,052,393,000 |  | 6,177,139,000 |  |  | 6,303,134,000 |  |
Modified interest rate increase | 1.00% |  |  |  |  |  |  |
TDRS Maturities | 40 years |  |  |  |  |  |  |
Allowance for loan losses | $ 143,757,000 |  | 28,443,000 |  | 123,022,000 | 31,532,000 | 34,154,000 | 37,439,000
Consumer | Credit Card and Other |  |  |  |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |  |  |  |
Loans, net of unearned income | 449,310,000 |  | 495,864,000 |  |  | 494,376,000 |  |
Allowance for loan losses | $ 18,117,000 |  | 13,266,000 |  | $ 19,327,000 | 12,168,000 | $ 12,662,000 | $ 12,727,000
Consumer | Permanent Mortgage |  |  |  |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |  |  |  |
TDR, reduction of interest rate by increment, basis points | 0.25% |  |  |  |  |  |  |
Consumer | Residential Real Estate |  |  |  |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |  |  |  |
Concentration risk, percentage | 19.00% |  |  |  |  |  |  |
Minimum | Commercial |  |  |  |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |  |  |  |
Forbearance agreements time period | 6 months |  |  |  |  |  |  |
Minimum | Consumer | Consumer Real Estate (a) |  |  |  |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |  |  |  |
Modified interest rate | 2.00% |  |  |  |  |  |  |
Modified interest rate time period | 5 years |  |  |  |  |  |  |
Maximum | Commercial |  |  |  |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |  |  |  |
Forbearance agreements time period | 12 months |  |  |  |  |  |  |
Maximum | Consumer | Consumer Real Estate (a) |  |  |  |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |  |  |  |
Modified interest rate time period | 5 years |  |  |  |  |  |  |
TRUPS |  |  |  |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |  |  |  |
Small bank and business loan, total asset maximum cap | $ 15,000,000,000 |  |  |  |  |  |  |
TRUPS | Commercial | Commercial, financial, and industrial |  |  |  |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |  |  |  |
Loans, net of unearned income | 209,177,000 |  | 218,287,000 |  |  |  |  |
Allowance for loan losses | $ 18,400,000 |  | 19,100,000 |  |  |  |  |
Heloc And Real Estate Installment Classes | Consumer | Consumer Real Estate (a) |  |  |  |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |  |  |  |
Modified interest rate increase | 2.00% |  |  |  |  |  |  |
TDR, reduction of interest rate by increment, basis points | 0.25% |  |  |  |  |  |  |
Heloc And Real Estate Installment Classes | Minimum | Consumer | Consumer Real Estate (a) |  |  |  |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |  |  |  |
Modified interest rate | 1.00% |  |  |  |  |  |  |
Modified interest rate time period | 5 years |  |  |  |  |  |  |
Heloc And Real Estate Installment Classes | Maximum | Consumer | Consumer Real Estate (a) |  |  |  |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |  |  |  |
Modified interest rate time period | 5 years |  |  |  |  |  |  |
Credit Card | Consumer | Credit Card and Other |  |  |  |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |  |  |  |
Loans, net of unearned income | $ 167,344,000 |  | 201,171,000 |  |  |  |  |
Credit card workout program, granted rate reduction | 0.00% |  |  |  |  |  |  |
Credit Card | Minimum | Consumer | Credit Card and Other |  |  |  |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |  |  |  |
Payment reductions, time period | 6 months |  |  |  |  |  |  |
Credit Card | Maximum | Consumer | Credit Card and Other |  |  |  |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |  |  |  |
Payment reductions, time period | 1 year |  |  |  |  |  |  |
Credit card workout program, term extension | 5 years |  |  |  |  |  |  |
Purchased credit-impaired loans |  |  |  |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |  |  |  |
Loans, net of unearned income |  |  |  |  |  | 68,799,000 |  |
Allowance for loan losses |  |  |  |  |  | 1,989,000 |  |
Allowance - purchased credit-impaired loans |  |  | 2,000,000.0 |  |  |  |  |
Allowance for loan and lease losses write-offs, net |  |  | 5,800,000 |  |  |  |  |
Provision for loan, lease, and other losses |  |  | 1,300,000 |  |  |  |  |
Purchased credit-impaired loans | Commercial | Commercial, financial, and industrial |  |  |  |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |  |  |  |
Loans, net of unearned income |  |  |  |  |  | 33,840,000 |  |
Allowance for loan losses |  |  |  |  |  | 854,000 |  |
Purchased credit-impaired loans | Consumer | Consumer Real Estate (a) |  |  |  |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |  |  |  |
Loans, net of unearned income |  |  |  |  |  | 26,829,000 |  |
Allowance for loan losses |  |  |  |  |  | 1,078,000 |  |
Purchased credit-impaired loans | Consumer | Credit Card and Other |  |  |  |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |  |  |  |
Loans, net of unearned income |  |  |  |  |  | 903,000 |  |
Allowance for loan losses |  |  |  |  |  | $ 57,000 |  |
PD Grade 1 | Commercial |  |  |  |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |  |  |  |
Lowest expected default probability | 1 |  |  |  |  |  |  |
Allowance for loan losses |  |  | 69,000 |  |  |  |  |
PD Grade 1 | Commercial | Commercial, financial, and industrial |  |  |  |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |  |  |  |
Loans, net of unearned income | $ 2,674,017,000 |  |  |  |  |  |  |
Loss | Commercial |  |  |  |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |  |  |  |
Commercial loan grades | 16 |  |  |  |  |  |  |
Loss | Maximum | Commercial |  |  |  |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |  |  |  |
Commercial loan grades | 16 |  |  |  |  |  |  |
Pass | Minimum | Commercial |  |  |  |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |  |  |  |
Commercial loan grades | 1 |  |  |  |  |  |  |
Pass | Maximum | Commercial |  |  |  |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |  |  |  |
Commercial loan grades | 12 |  |  |  |  |  |  |
Special Mention | Commercial |  |  |  |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |  |  |  |
Commercial loan grades | 13 |  |  |  |  |  |  |
Special Mention | Minimum | Commercial |  |  |  |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |  |  |  |
Commercial loan grades | 13 |  |  |  |  |  |  |
Substandard | Commercial |  |  |  |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |  |  |  |
Commercial loan grades | 14 |  |  |  |  |  |  |
Doubtful | Commercial |  |  |  |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |  |  |  |
Commercial loan grades | 15 |  |  |  |  |  |  |
Loan Reassessed | Minimum | Commercial |  |  |  |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |  |  |  |
Loans, net of unearned income | $ 1,000,000 |  |  |  |  |  |  |
PD Grade 13 | Commercial |  |  |  |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |  |  |  |
Allowance for loan losses |  |  | $ 8,142,000 |  |  |  |  |
PD Grade 13 | Commercial | Commercial, financial, and industrial |  |  |  |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |  |  |  |
Loans, net of unearned income | 336,048,000 |  |  |  |  |  |  |
PD Grade 13 | Minimum | Commercial |  |  |  |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |  |  |  |
Loans, net of unearned income | $ 500,000 |  |  |  |  |  |  |
LGD Grade 1 | Minimum | Commercial |  |  |  |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |  |  |  |
Commercial loan grades | 1 |  |  |  |  |  |  |
LGD Grade 12 | Maximum | Commercial |  |  |  |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |  |  |  |
Commercial loan grades | 12 |  |  |  |  |  |  |
Paycheck Protection Plan | Commercial | Commercial, financial, and industrial |  |  |  |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |  |  |  |
Loans, net of unearned income | $ 2,100,000,000 |  |  |  |  |  |  |
[1] | June 30, 2020 and December 31, 2019 include $16.9 million and $18.8 million, respectively, of held-to-maturity consumer mortgage loans secured by residential real estate in process of foreclosure.

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