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Loans and Loans Held for Sale - Restructured Loans for Periods Presented (Details) - USD ($) $ in Thousands | 3 Months Ended | 12 Months Ended
--- | --- | ---
Sep. 30, 2019 | Dec. 31, 2019 | Dec. 31, 2018
Financing Receivable, Troubled Debt Restructuring [Line Items] |  |  |  |
Restructured loans | [1] |  | $ 32,206 | $ 11,384
Commercial real estate |  |  |  |
Financing Receivable, Troubled Debt Restructuring [Line Items] |  |  |  |
Restructured loans | [1] |  | 25,159 | 269
Commercial and industrial |  |  |  |
Financing Receivable, Troubled Debt Restructuring [Line Items] |  |  |  |
Restructured loans | [1] |  | 5,661 | 9,890
Residential mortgage |  |  |  |
Financing Receivable, Troubled Debt Restructuring [Line Items] |  |  |  |
Restructured loans | [1] |  | 340 | 374
Home equity |  |  |  |
Financing Receivable, Troubled Debt Restructuring [Line Items] |  |  |  |
Restructured loans | [1] |  | 1,037 | 847
Installment and other consumer |  |  |  |
Financing Receivable, Troubled Debt Restructuring [Line Items] |  |  |  |
Restructured loans | [1],[2] |  | 11 | 4
Performing TDRs |  |  |  |
Financing Receivable, Troubled Debt Restructuring [Line Items] |  |  |  |
Restructured loans |  |  | 36,960 | 16,786
Performing TDRs | Commercial real estate |  |  |  |
Financing Receivable, Troubled Debt Restructuring [Line Items] |  |  |  |
Restructured loans |  | $ 20,200 | 22,233 | 2,054
Performing TDRs | Commercial and industrial |  |  |  |
Financing Receivable, Troubled Debt Restructuring [Line Items] |  |  |  |
Restructured loans |  |  | 6,909 | 7,026
Performing TDRs | Commercial construction |  |  |  |
Financing Receivable, Troubled Debt Restructuring [Line Items] |  |  |  |
Restructured loans |  |  | 1,425 | 1,912
Performing TDRs | Residential mortgage |  |  |  |
Financing Receivable, Troubled Debt Restructuring [Line Items] |  |  |  |
Restructured loans |  |  | 2,013 | 2,214
Performing TDRs | Home equity |  |  |  |
Financing Receivable, Troubled Debt Restructuring [Line Items] |  |  |  |
Restructured loans |  |  | 4,371 | 3,568
Performing TDRs | Installment and other consumer |  |  |  |
Financing Receivable, Troubled Debt Restructuring [Line Items] |  |  |  |
Restructured loans |  |  | 9 | 12
Nonperforming TDRs |  |  |  |
Financing Receivable, Troubled Debt Restructuring [Line Items] |  |  |  |
Restructured loans |  |  | 8,912 | 11,088
Nonperforming TDRs | Commercial real estate |  |  |  |
Financing Receivable, Troubled Debt Restructuring [Line Items] |  |  |  |
Restructured loans |  |  | 6,713 | 1,139
Nonperforming TDRs | Commercial and industrial |  |  |  |
Financing Receivable, Troubled Debt Restructuring [Line Items] |  |  |  |
Restructured loans |  |  | 695 | 6,646
Nonperforming TDRs | Commercial construction |  |  |  |
Financing Receivable, Troubled Debt Restructuring [Line Items] |  |  |  |
Restructured loans |  |  | 0 | 406
Nonperforming TDRs | Residential mortgage |  |  |  |
Financing Receivable, Troubled Debt Restructuring [Line Items] |  |  |  |
Restructured loans |  |  | 822 | 1,543
Nonperforming TDRs | Home equity |  |  |  |
Financing Receivable, Troubled Debt Restructuring [Line Items] |  |  |  |
Restructured loans |  |  | 678 | 1,349
Nonperforming TDRs | Installment and other consumer |  |  |  |
Financing Receivable, Troubled Debt Restructuring [Line Items] |  |  |  |
Restructured loans |  |  | 4 | 5
Total TDRs |  |  |  |
Financing Receivable, Troubled Debt Restructuring [Line Items] |  |  |  |
Restructured loans |  |  | 45,872 | 27,874
Total TDRs | Commercial real estate |  |  |  |
Financing Receivable, Troubled Debt Restructuring [Line Items] |  |  |  |
Restructured loans |  |  | 28,946 | 3,193
Total TDRs | Commercial and industrial |  |  |  |
Financing Receivable, Troubled Debt Restructuring [Line Items] |  |  |  |
Restructured loans |  |  | 7,604 | 13,672
Total TDRs | Commercial construction |  |  |  |
Financing Receivable, Troubled Debt Restructuring [Line Items] |  |  |  |
Restructured loans |  |  | 1,425 | 2,318
Total TDRs | Residential mortgage |  |  |  |
Financing Receivable, Troubled Debt Restructuring [Line Items] |  |  |  |
Restructured loans |  |  | 2,835 | 3,757
Total TDRs | Home equity |  |  |  |
Financing Receivable, Troubled Debt Restructuring [Line Items] |  |  |  |
Restructured loans |  |  | 5,049 | 4,917
Total TDRs | Installment and other consumer |  |  |  |
Financing Receivable, Troubled Debt Restructuring [Line Items] |  |  |  |
Restructured loans |  |  | $ 13 | $ 17
[1] | Excludes loans that were fully paid off or fully charged-off by period end. The pre-modification balance represents the balance outstanding prior to modification. The post-modification balance represents the outstanding balance at period end.
[2] | Consumer bankruptcy loans where the debt has been legally discharged through the bankruptcy court and not reaffirmed.

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