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Loans and Loans Held for Sale - Additional Information (Details) $ in Thousands |  |  | 3 Months Ended | 6 Months Ended | 12 Months Ended |  |  |
--- | --- | --- | --- | --- | --- | --- | --- | ---
Jun. 30, 2020 USD ($) loan | Dec. 31, 2019 USD ($) | Jun. 30, 2020 USD ($) loan | Mar. 31, 2020 USD ($) | Jun. 30, 2019 USD ($) loan | Jun. 30, 2020 USD ($) note loan | Jun. 30, 2019 USD ($) loan | Dec. 31, 2019 USD ($) | Jan. 01, 2020 USD ($) | Mar. 31, 2019 USD ($) | Dec. 31, 2018 USD ($)
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Loans, net of unearned income |  | $ 16,700 | $ 4,600 | $ 16,700 |  |  | $ 16,700 |  | $ 4,600 |  |  |
Purchase accounting fair value adjustments |  | 10,500 | 12,300 |  |  |  |  |  |  |  |  |
Total loans |  |  |  |  |  |  |  |  |  | $ 7,074,928 |  |
Threshold period of satisfactory performance for troubled debt restructuring to be restored to accruing status |  |  |  |  |  |  | 6 months |  |  |  |  |
Restructured loans | [1],[2] |  |  | 1,304 |  | $ 6,427 | $ 7,853 | $ 11,248 |  |  |  |
Allowance for credit loss |  | $ 114,609 | $ 62,224 | $ 114,609 | $ 96,850 | $ 61,479 | $ 114,609 | $ 61,479 | $ 62,224 | $ 62,224 | $ 61,409 | $ 60,996
Number of troubled debt restructuring loans returned to accruing status | loan |  |  |  | 4 |  | 3 | 4 | 4 |  |  |  |
Amount of trouble debt restructuring loans returned to accruing status |  |  |  | $ 100 |  | $ 100 | $ 100 | $ 1,800 |  |  |  |
Number of loans | loan | [2] |  |  | 11 |  | 14 | 20 | 25 |  |  |  |
Number of commitments to lend additional funds on TDRs | loan |  | 22 |  | 22 |  |  | 22 |  |  |  |  |
Commitments to lend additional funds on TDRs |  | $ 3,100 |  | $ 3,100 |  |  | $ 3,100 |  |  |  |  |
Minimum period of loan payment defaults following restructure for TDRs to be in default |  |  |  |  |  |  | 90 days |  |  |  |  |
Number of defaulted TDRs that were restructured within the last twelve months prior to defaulting | loan |  |  |  | 1 |  | 0 | 11 | 0 |  |  |  |
Amount of defaulted TDRs that were restructured within the last twelve months prior to defaulting |  |  |  | $ 100 |  |  | $ 21,100 |  |  |  |  |
Number of notes related to individual customer resulting in an increase in defaulted troubled debt restructuring loans due to Covid-19 | note |  |  |  |  |  |  | 5 |  |  |  |  |
Commercial |  |  |  |  |  |  |  |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Percentage of commercial loans in total portfolio loans |  | 78.80% | 77.20% | 78.80% |  |  | 78.80% |  | 77.20% |  |  |
Commercial loans |  |  | $ 5,512,796 |  |  |  |  |  | $ 5,512,796 |  |  |
Commercial real estate |  |  |  |  |  |  |  |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Restructured loans | [1] |  |  | $ 0 |  | $ 6,090 | $ 2,210 | $ 6,090 |  |  |  |
Allowance for credit loss |  |  |  |  |  | $ 32,836 |  | $ 32,836 |  |  | 34,903 | 33,707
Number of loans | loan |  |  |  | 0 |  | 3 | 1 | 3 |  |  |  |
Commercial real estate | Commercial |  |  |  |  |  |  |  |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Commercial loans |  |  | 3,416,518 |  |  |  |  |  | 3,416,518 |  |  |
Allowance for credit loss |  | $ 57,730 | 30,577 | $ 57,730 | 42,611 |  | $ 57,730 |  | 30,577 |  |  |
Commercial and industrial |  |  |  |  |  |  |  |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Restructured loans | [1] |  |  | $ 102 |  | $ 0 | $ 2,170 | $ 4,529 |  |  |  |
Allowance for credit loss |  |  |  |  |  | $ 13,227 |  | $ 13,227 |  |  | $ 11,996 | $ 11,596
Number of loans | loan |  |  |  | 2 |  | 0 | 3 | 1 |  |  |  |
Commercial and industrial | Commercial |  |  |  |  |  |  |  |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Commercial loans |  |  | 1,720,833 |  |  |  |  |  | 1,720,833 |  |  |
Allowance for credit loss |  | 19,164 | 15,681 | $ 19,164 | 19,870 |  | $ 19,164 |  | 15,681 |  |  |
Customer fraud |  |  |  |  |  |  |  |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Total loans |  | 15,100 |  | 15,100 |  |  | 15,100 |  |  |  |  |
CRE and commercial construction | Commercial |  |  |  |  |  |  |  |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Commercial loans |  | $ 3,800,000 | $ 3,800,000 | $ 3,800,000 |  |  | $ 3,800,000 |  | $ 3,800,000 |  |  |
Combined percentage of commercial real estate and commercial construction in total commercial loans |  | 64.00% | 68.80% | 64.00% |  |  | 64.00% |  | 68.80% |  |  |
Combined percentage of commercial real estate and commercial construction in total portfolio loans |  | 50.40% | 53.10% | 50.40% |  |  | 50.40% |  | 53.10% |  |  |
Concentration risk percentage of commercial real estate and commercial construction |  |  |  |  |  |  | 0.00% |  | 0.00% |  |  |
Maximum concentration of commercial real estate and commercial construction portfolio in loans (in excess of) |  | 14.00% | 11.00% | 14.00% |  |  | 14.00% |  | 11.00% |  |  |
Out of market exposure of combined portfolio (percent) |  | 5.70% | 5.40% | 5.70% |  |  | 5.70% |  | 5.40% |  |  |
Percentage of total loans out-of-state excluding contiguous states |  | 3.00% | 2.90% | 3.00% |  |  | 3.00% |  | 2.90% |  |  |
CARES Act, Paycheck Protection Program Loans |  |  |  |  |  |  |  |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Total loans |  | $ 547,600 |  | $ 547,600 |  |  | $ 547,600 |  |  |  |  |
Restructured loans |  |  |  |  |  |  | $ 1,400,000 |  |  |  |  |
Number of loans | loan |  |  |  |  |  |  | 2,360 |  |  |  |  |
Nonperforming TDRs | Commercial real estate |  |  |  |  |  |  |  |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Restructured loans |  |  |  |  | $ 20,500 |  | $ 20,500 |  |  |  |  |
Allowance for credit loss |  | $ 600 |  | 600 |  |  | 600 |  |  |  |  |
Nonperforming TDRs | Commercial and industrial |  |  |  |  |  |  |  |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Restructured loans |  |  |  |  |  |  | 4,300 |  |  |  |  |
Nonperforming TDRs | Customer fraud |  |  |  |  |  |  |  |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Restructured loans |  |  |  | $ 10,900 |  |  | $ 10,900 |  |  |  |  |
[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] | Refer to Note 1, Basis of Presentation for details of reclassification of our portfolio segments related to the adoption of ASU 2016-13 Financial Instruments - Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instrument.

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