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Loans and Loans Held for Sale - Additional Information (Details) $ in Thousands | 3 Months Ended | 12 Months Ended
--- | --- | ---
Sep. 30, 2019 USD ($) | Dec. 31, 2019 USD ($) loan | Dec. 31, 2018 USD ($) loan
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |
Unearned income on loans and leases receivable |  |  | $ 4,600 | $ 5,300
Net unamortized discount related to purchase accounting fair value adjustments |  |  | 12,300 | 3,300
Loans receivable, net |  |  | 7,142,408 | 5,949,019
Restructured loans | [1] |  | $ 32,206 | $ 11,384
Number of commitments to lend additional funds | loan |  |  | 24 | 6
Commitment to lend additional funds |  |  | $ 4,600 | $ 11,600
Number of TDRs returned back to accruing status | loan |  |  | 6 | 0
Financial receivable trouble debt restructuring reclassified to accruing trouble debt restructuring status |  |  | $ 500 |
Minimum period of loan payment defaults following restructure for TDRs to be in default |  |  | 90 days |
Number of TDRs defaulted that were restructured within the last 12 months prior to defaulting | loan |  |  | 0 | 4
Financial receivable defaulted trouble debt restructuring loans restructured within twelve months prior to defaulting |  |  |  | $ 4,400
Increase in nonperforming assets |  |  | $ 8,400 |
Nonperforming assets |  |  | $ 57,582 | $ 49,165
Commercial |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |
Percentage of commercial loans in total portfolio loans |  |  | 77.00% | 79.00%
Loans recorded investment |  |  | $ 5,512,796 | $ 4,672,445
Restructured loans |  |  | 20,200 |
Commercial real estate |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |
Loans receivable, net |  |  | 3,416,518 | 2,921,832
Restructured loans | [1] |  | 25,159 | 269
Commercial real estate | Commercial |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |
Loans recorded investment |  |  | 3,416,518 | 2,921,832
Commercial and industrial |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |
Loans receivable, net |  |  | 1,720,833 | 1,493,416
Restructured loans | [1] |  | $ 5,661 | 9,890
Number of nonperforming, impaired loans paid off during the period | loan |  |  | 1 |
Balance of nonperforming, impaired loans paid off during the period |  |  | $ 10,000 |
Commercial and industrial | Commercial |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |
Loans recorded investment |  |  | 1,720,833 | 1,493,416
Commercial construction |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |
Loans receivable, net |  |  | 375,445 | 257,197
Commercial construction | Commercial |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |
Loans recorded investment |  |  | 375,445 | 257,197
Residential mortgage |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |
Loans receivable, net |  |  | 998,585 | 726,679
Restructured loans | [1] |  | 340 | 374
Home equity |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |
Loans receivable, net |  |  | 538,348 | 471,562
Restructured loans | [1] |  | 1,037 | 847
Installment and other consumer |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |
Loans receivable, net |  |  | 79,033 | 67,546
Restructured loans | [1],[2] |  | 11 | 4
Consumer construction |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |
Loans receivable, net |  |  | 8,390 | 8,416
CRE and Commercial Construction | Commercial |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |
Loans recorded investment |  |  | $ 3,800,000 | $ 3,200,000
Combined percentage of commercial real estate and commercial construction in total commercial loans |  |  | 69.00% | 68.00%
Combined percentage of commercial real estate and commercial construction in total portfolio loans |  |  | 53.00% | 53.00%
Concentration risk percentage |  |  | 0.00% | 0.00%
Maximum concentration of commercial real estate and commercial construction portfolio in loans |  |  | 11.00% | 14.00%
Out-of-state exposure of combined portfolio |  |  | 5.40% | 5.40%
Percentage of total loans out-of-state excluding contiguous states |  |  | 2.90% | 2.90%
DNB |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |
Loans receivable, net |  |  | $ 899,300 | $ 909,000
DNB | Commercial real estate |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |
Loans receivable, net |  |  | 455,600 |
DNB | Commercial and industrial |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |
Loans receivable, net |  |  | 85,400 |
DNB | Commercial construction |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |
Loans receivable, net |  |  | 77,100 |
DNB | Residential mortgage |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |
Loans receivable, net |  |  | 219,700 |
DNB | Home equity |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |
Loans receivable, net |  |  | 56,400 |
DNB | Installment and other consumer |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |
Loans receivable, net |  |  | 4,100 |
DNB | Consumer construction |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |
Loans receivable, net |  |  | 1,000 |
Performing TDRs |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |
Restructured loans |  |  | 36,960 | 16,786
Performing TDRs | Commercial real estate |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |
Restructured loans |  | $ 20,200 | 22,233 | 2,054
Performing TDRs | Commercial and industrial |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |
Restructured loans |  |  | 6,909 | 7,026
Performing TDRs | Commercial construction |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |
Restructured loans |  |  | 1,425 | 1,912
Performing TDRs | Residential mortgage |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |
Restructured loans |  |  | 2,013 | 2,214
Performing TDRs | Home equity |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |
Restructured loans |  |  | 4,371 | 3,568
Performing TDRs | Installment and other consumer |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |
Restructured loans |  |  | $ 9 | $ 12
[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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