Securities - Amortized Cost and Fair Value of Securities with Gross Unrealized Gains and Losses (Detail) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$ 300,602	$ 220,904
Gross Unrealized Gains	7,350	1,769
Gross Unrealized Losses	(140)	(380)
Fair Value	307,812	222,293
U.S. Treasury [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost		10,023
Gross Unrealized Gains		10
Gross Unrealized Losses		(12)
Fair Value		10,021
U.S. Government Agencies [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	122,514	61,882
Gross Unrealized Gains	1,857	584
Gross Unrealized Losses	(130)	(21)
Fair Value	124,241	62,445
Mortgage-backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	110,828	94,998
Gross Unrealized Gains	2,228	426
Gross Unrealized Losses		(227)
Fair Value	113,056	95,197
State and Local Governments [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	67,260	54,001
Gross Unrealized Gains	3,265	749
Gross Unrealized Losses	(10)	(120)
Fair Value	$ 70,515	$ 54,630

Amount, before tax, of unrealized gain in accumulated other comprehensive income (AOCI) on 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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Amount, before tax, of unrealized loss in accumulated other comprehensive income (AOCI) on 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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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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Amount 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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