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Loans and Allowance for Credit Losses - Loans Outstanding and Aging Analysis (Details) - USD ($) | 12 Months Ended
--- | ---
Dec. 31, 2020 | Dec. 31, 2019 | Dec. 31, 2018
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Total past due | $ 2,705,000 | $ 1,648,000 |
Current | 2,085,851,000 | 1,841,638,000 |
Total loans | 2,088,556,000 | 1,843,286,000 |
Non-accrual loans | 9,233,000 | 226,000 |
Non-accrual loans with no allowance | 9,233,000 | 226,000 |
Loans past due more than 90 days still accruing | 0 | 0 |
Nonaccrual loans earning interest on cash basis | 0 | 0 |
Nonaccrual interest income | 0 | 0 | $ 0
Accrued interest writeoff | 36,000 |  |
30-59 days past due |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Total past due | 2,083,000 | 1,288,000 |
60-89 days past due |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Total past due | 622,000 | 193,000 |
90 days or more past due |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Total past due | 0 | 167,000 |
Commercial | Commercial and industrial |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Total past due | 0 | 1,000 |
Current | 498,408,000 | 246,686,000 |
Total loans | 498,408,000 | 246,687,000 |
Non-accrual loans | 0 | 0 |
Non-accrual loans with no allowance | 0 | 0 |
Commercial | Commercial and industrial | 30-59 days past due |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Total past due | 0 | 1,000 |
Commercial | Commercial and industrial | 60-89 days past due |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Total past due | 0 | 0 |
Commercial | Commercial and industrial | 90 days or more past due |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Total past due | 0 | 0 |
Commercial real estate | Commercial real estate, owner-occupied |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Total past due | 0 | 0 |
Current | 304,963,000 | 308,824,000 |
Total loans | 304,963,000 | 308,824,000 |
Non-accrual loans | 7,147,000 | 0 |
Non-accrual loans with no allowance | 7,147,000 | 0 |
Commercial real estate | Commercial real estate, owner-occupied | 30-59 days past due |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Total past due | 0 | 0 |
Commercial real estate | Commercial real estate, owner-occupied | 60-89 days past due |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Total past due | 0 | 0 |
Commercial real estate | Commercial real estate, owner-occupied | 90 days or more past due |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Total past due | 0 | 0 |
Commercial real estate | Commercial real estate, investor-owned |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Total past due | 1,673,000 | 1,001,000 |
Current | 959,535,000 | 945,316,000 |
Total loans | 961,208,000 | 946,317,000 |
Non-accrual loans | 1,610,000 | 0 |
Non-accrual loans with no allowance | 1,610,000 | 0 |
Commercial real estate | Commercial real estate, investor-owned | 30-59 days past due |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Total past due | 1,673,000 | 1,001,000 |
Commercial real estate | Commercial real estate, investor-owned | 60-89 days past due |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Total past due | 0 | 0 |
Commercial real estate | Commercial real estate, investor-owned | 90 days or more past due |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Total past due | 0 | 0 |
Commercial real estate | Construction |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Total past due | 0 | 0 |
Current | 73,046,000 | 61,095,000 |
Total loans | 73,046,000 | 61,095,000 |
Non-accrual loans | 0 | 0 |
Non-accrual loans with no allowance | 0 | 0 |
Commercial real estate | Construction | 30-59 days past due |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Total past due | 0 | 0 |
Commercial real estate | Construction | 60-89 days past due |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Total past due | 0 | 0 |
Commercial real estate | Construction | 90 days or more past due |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Total past due | 0 | 0 |
Residential loans | Home equity |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Total past due | 274,000 | 544,000 |
Current | 104,539,000 | 115,480,000 |
Total loans | 104,813,000 | 116,024,000 |
Non-accrual loans | 459,000 | 168,000 |
Non-accrual loans with no allowance | 459,000 | 168,000 |
Residential loans | Home equity | 30-59 days past due |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Total past due | 274,000 | 279,000 |
Residential loans | Home equity | 60-89 days past due |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Total past due | 0 | 98,000 |
Residential loans | Home equity | 90 days or more past due |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Total past due | 0 | 167,000 |
Residential loans | Other residential |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Total past due | 0 | 0 |
Current | 123,395,000 | 136,657,000 |
Total loans | 123,395,000 | 136,657,000 |
Non-accrual loans | 0 | 0 |
Non-accrual loans with no allowance | 0 | 0 |
Residential loans | Other residential | 30-59 days past due |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Total past due | 0 | 0 |
Residential loans | Other residential | 60-89 days past due |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Total past due | 0 | 0 |
Residential loans | Other residential | 90 days or more past due |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Total past due | 0 | 0 |
Consumer loans | Installment and other consumer |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Total past due | 758,000 | 102,000 |
Current | 21,965,000 | 27,580,000 |
Total loans | 22,723,000 | 27,682,000 |
Non-accrual loans | 17,000 | 58,000 |
Non-accrual loans with no allowance | 17,000 | 58,000 |
Consumer loans | Installment and other consumer | 30-59 days past due |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Total past due | 136,000 | 7,000 |
Consumer loans | Installment and other consumer | 60-89 days past due |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Total past due | 622,000 | 95,000 |
Consumer loans | Installment and other consumer | 90 days or more past due |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Total past due | $ 0 | $ 0 |

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