Securities - Amortized Cost and Fair Value of Securities by Contractual Maturity (Detail) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Investments Debt And Equity Securities [Abstract]
Amortized Cost, Due in one year or less	$ 9,145
Amortized Cost, Due after one year through five years	19,813
Amortized Cost, Due after five years through ten years	30,263
Amortized Cost, Due after ten years	179,522
Amortized Cost, Mortgage-backed securities	97,407
Amortized Cost, Total securities available for sale	336,150	$ 336,316
Fair Value, Due in one year or less	9,250
Fair Value, Due after one year through five years	20,100
Fair Value, Due after five years through ten years	32,010
Fair Value, Due after ten years	193,877
Fair Value, Mortgage-backed securities	101,587
Fair Value, Total securities available for sale	$ 356,824	$ 363,464

Amortized cost of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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