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Loans - Narrative (Details) | 12 Months Ended
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Dec. 31, 2021 USD ($) loan | Dec. 31, 2020 USD ($) loan | Dec. 31, 2019 USD ($) loan
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Loans held for investment at fair value | $ 0 | $ 17,011,000 |
Loans held for investment | 5,231,331,000 | 5,707,762,000 |
Net deferred loan fees | 9,600,000 | 13,700,000 |
Accrued interest | 15,900,000 | 20,300,000 |
Increase (decrease) in reserve | (25,100,000) |  |
Decrease in reserves due to qualitative factor changes across risk pools | 19,600,000 |  |
Provision expense |  | 39,800,000 |
Provision expense as a result of COVID-19 |  | 27,500,000 |
Provision expense as a result of COVID-19 due to effects of individually evaluated loans |  | $ 8,100,000 |
Number of significant loan write-offs | loan |  | 4 |
Charge-off as a result of COVID-19 |  | $ 6,600,000 |
Nonaccrual mortgage loans held for sale recorded at fair value | $ 1,800,000 | $ 681,000 |
Number of loans that defaulted | loan | 1 | 0 | 2
Nonperforming Financial Instruments |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Gross interest income that would have been recorded | $ 1,900,000 | $ 1,500,000 | $ 1,500,000
Interest income | 0 | 0 | 0
Outstanding principal balance | 9,000 |  | $ 117,000
Paycheck Protection Program |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Loans held for investment | 105,800,000 | 546,500,000 |
Net deferred loan fees | 3,000,000 | 9,600,000 |
Debt instrument forgiveness | 648,400,000 |  |
Real estate |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Loans held for investment | 3,133,334,000 | 2,787,908,000 |
Real estate | Commercial real estate |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Loans held for investment at fair value | 0 | 17,000,000 |
Loans held for investment | 1,693,512,000 | 1,370,928,000 |
Commercial Portfolio Segment |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Loans held for investment | $ 1,454,235,000 | $ 1,817,862,000 |

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