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Fair Value Measurements - Additional Information (Detail) - USD ($) $ in Millions | Sep. 30, 2020 | Dec. 31, 2019
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Mortgage Loans Held For Sale |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Notional amount | $ 256.6 | $ 34.3
IRLCs |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Notional amount | $ 329.9 | $ 64.7

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