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Commitments and contingencies - Summary of Financial Instruments with Off-Balance Sheet Credit Risk (Details) - USD ($) $ in Thousands | Sep. 30, 2020 | Dec. 31, 2019
--- | --- | ---
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items] |  |
Balance at end of period | $ 1,837,309 | $ 1,105,742
Commitments to extend credit, excluding interest rate lock commitments |  |
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items] |  |
Balance at end of period | 1,819,070 | 1,086,173
Letters of credit |  |
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items] |  |
Balance at end of period | $ 18,239 | $ 19,569

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- Definition The face amount of financial liabilities, which are not recognized in the financial statements (off-balance sheet) because they fail to meet some other criterion for recognition. + References No definition available. + Details
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- Definition Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. + References No definition available. + Details
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