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Securities - Amortized Cost and Fair Value of Debt Securities, by Contractual Maturity (Detail) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Available For Sale Securities Debt Maturities [Abstract]
Amortized Cost, One year or less	$ 1,044
Amortized Cost, After one year through five years	63,793
Amortized Cost, After five years through ten years	123,275
Amortized Cost, After ten years	1,662
Amortized Cost, Total	189,774
Amortized Cost, Mortgage-backed securities	110,828
Amortized Cost	300,602	$ 220,904
Fair Value, One year or less	1,054
Fair Value, After one year through five years	65,323
Fair Value, After five years through ten years	126,630
Fair Value, After ten years	1,749
Fair Value, Total	194,756
Fair Value, Mortgage-backed securities	113,056
Total, Fair Value	$ 307,812	$ 222,293

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