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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, 2021 USD ($) relationship loan | Dec. 31, 2020 USD ($) | Jun. 30, 2021 USD ($) relationship loan | Mar. 31, 2021 USD ($) | Jun. 30, 2020 USD ($) loan | Jun. 30, 2021 USD ($) relationship loan | Jun. 30, 2020 USD ($) loan | Dec. 31, 2020 USD ($) loan
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |  |  |  |
Unearned income | $ 16,500 | $ 16,000 | $ 16,500 |  |  | $ 16,500 |  | $ 16,000
Purchase accounting fair value adjustments | 6,900 | 8,600 |  |  |  |  |  |
Total loans | 6,897,715 | 7,108,248 | 6,897,715 |  |  | 6,897,715 |  | 7,108,248
Loans held for investment, outstanding balance | $ 7,007,351 | 7,225,860 | $ 7,007,351 |  |  | $ 7,007,351 |  | 7,225,860
Threshold period of satisfactory performance for troubled debt restructuring to be restored to accruing status |  |  |  |  |  | 6 months |  |
Number of troubled debt restructuring loans returned to accruing status | loan |  |  | 4 |  | 4 | 5 | 4 |
Financing receivable, troubled debt restructuring, returned to accruing status |  |  | $ 500 |  | $ 100 | $ 500 | $ 100 |
Number of commitments to lend additional funds on TDRs | loan | 14 |  | 14 |  |  | 14 |  |
Commitments to lend additional funds on TDRs | $ 700 |  | $ 700 |  |  | $ 700 |  |
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 |  |  | 0 |  | 1 |  | 11 |
Amount of defaulted TDRs that were restructured within the last twelve months prior to defaulting |  |  |  |  | $ 100 |  | $ 21,100 |
Number of commercial real estate relationships | relationship | 3 |  | 3 |  |  | 3 |  |
Restructured loans |  |  | $ 1,377 |  | 1,303 | $ 8,159 | 7,852 |
Commercial |  |  |  |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |  |  |  |
Loans held for investment, outstanding balance | $ 5,499,044 | $ 5,673,707 | $ 5,499,044 |  |  | $ 5,499,044 |  | $ 5,673,707
Financing receivable, before allowance for credit loss, reclassification during period |  |  |  | $ 90,200 |  |  |  |
Percentage of commercial loans in total portfolio loans | 78.50% | 78.50% | 78.50% |  |  | 78.50% |  | 78.50%
Commercial | CARES Act, Paycheck Protection Program Loans |  |  |  |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |  |  |  |
Number of modified loans | loan |  |  |  |  |  | 42 |  | 52
Modified loans |  |  |  |  |  | $ 68,700 |  | $ 195,600
Business banking portfolio |  |  |  |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |  |  |  |
Loans held for investment, outstanding balance | $ 1,100,000 | $ 1,200,000 | $ 1,100,000 |  |  | 1,100,000 |  | 1,200,000
Consumer |  |  |  |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |  |  |  |
Loans held for investment, outstanding balance | 1,508,307 | 1,552,153 | 1,508,307 |  |  | 1,508,307 |  | 1,552,153
Financing receivable, before allowance for credit loss, reclassification during period |  |  |  | $ 23,200 |  |  |  |
CARES Act, Paycheck Protection Program Loans | Commercial |  |  |  |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |  |  |  |
Total loans | 336,100 | 465,000 | 336,100 |  |  | 336,100 |  | 465,000
Commercial real estate | Commercial |  |  |  |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |  |  |  |
Loans held for investment, outstanding balance | 2,740,296 | 2,791,947 | 2,740,296 |  |  | 2,740,296 |  | 2,791,947
Restructured loans |  |  | 0 |  | 0 | 0 | 2,210 |
Commercial real estate | Business banking portfolio |  |  |  |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |  |  |  |
Loans held for investment, outstanding balance | 506,200 | 453,000 | 506,200 |  |  | 506,200 |  | 453,000
Commercial and industrial | Commercial |  |  |  |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |  |  |  |
Loans held for investment, outstanding balance | 1,546,247 | 1,559,552 | 1,546,247 |  |  | 1,546,247 |  | 1,559,552
Restructured loans |  |  | 0 |  | 75 | 6,229 | 2,143 |
Commercial and industrial | Business banking portfolio |  |  |  |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |  |  |  |
Loans held for investment, outstanding balance | 228,100 | 394,900 | 228,100 |  |  | 228,100 |  | 394,900
Commercial construction | Commercial |  |  |  |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |  |  |  |
Loans held for investment, outstanding balance | 467,871 | 466,077 | 467,871 |  |  | 467,871 |  | 466,077
Restructured loans |  |  | 0 |  | 701 | 0 | 2,572 |
Commercial construction | Business banking portfolio |  |  |  |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |  |  |  |
Loans held for investment, outstanding balance | 10,300 | 8,200 | 10,300 |  |  | 10,300 |  | 8,200
Consumer real estate | Business banking portfolio |  |  |  |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |  |  |  |
Loans held for investment, outstanding balance | 326,200 |  | 326,200 |  |  | 326,200 |  |
Consumer real estate | Consumer |  |  |  |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |  |  |  |
Loans held for investment, outstanding balance | 1,093,878 | 1,167,332 | 1,093,878 |  |  | 1,093,878 |  | 1,167,332
Restructured loans |  |  | 247 |  | 500 | 720 | 900 |
Other consumer | Business banking portfolio |  |  |  |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |  |  |  |
Loans held for investment, outstanding balance | 30 |  | 30 |  |  | 30 |  |
Other consumer | Consumer |  |  |  |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |  |  |  |
Loans held for investment, outstanding balance | 88,184 | 80,885 | 88,184 |  |  | 88,184 |  | 80,885
Restructured loans |  |  | 0 |  | 0 | 0 | 0 |
Business banking | Commercial |  |  |  |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |  |  |  |
Loans held for investment, outstanding balance | 1,070,875 | 1,160,067 | 1,070,875 |  |  | 1,070,875 |  | 1,160,067
Restructured loans |  |  | 1,130 |  | $ 27 | 1,210 | $ 27 |
Business banking | Consumer |  |  |  |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |  |  |  |
Loans held for investment, outstanding balance |  | 303,900 |  |  |  |  |  | 303,900
CRE and commercial construction | Commercial |  |  |  |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |  |  |  |
Loans held for investment, outstanding balance | $ 3,700,000 | $ 3,700,000 | $ 3,700,000 |  |  | $ 3,700,000 |  | $ 3,700,000
Combined percentage of commercial real estate and commercial construction in total commercial loans | 67.70% | 65.60% | 67.70% |  |  | 67.70% |  | 65.60%
Combined percentage of commercial real estate and commercial construction in total portfolio loans | 53.20% | 51.50% | 53.20% |  |  | 53.20% |  | 51.50%
Out of market exposure of combined portfolio (percent) | 5.40% | 5.90% | 5.40% |  |  | 5.40% |  | 5.90%
Percentage of total loans out-of-state excluding contiguous states | 2.90% | 3.00% | 2.90% |  |  | 2.90% |  | 3.00%
Nonperforming TDRs |  |  |  |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |  |  |  |
Financing receivable, nonperforming assets, period increase (decrease) |  |  |  |  |  | $ 34,200 |  |
Nonperforming TDRs | Commercial real estate | Commercial |  |  |  |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |  |  |  |
Restructured loans |  |  |  |  |  | 14,400 |  |
Amount charged down |  |  |  |  |  | 4,900 |  |
Nonperforming TDRs | Commercial and industrial | Commercial |  |  |  |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |  |  |  |
Amount charged down |  |  |  |  |  | $ 3,900 |  |

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