Securities - Amortized Cost and Fair Value of Securities with Gross Unrealized Gains and Losses (Detail) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$ 352,794	$ 300,602
Gross Unrealized Gains	4,817	7,350
Gross Unrealized Losses	(4,637)	(140)
Fair Value	352,974	307,812
U.S. Treasury [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	44,059
Gross Unrealized Losses	(734)
Fair Value	43,325
U.S. Government Agencies [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	131,419	122,514
Gross Unrealized Gains	1,378	1,857
Gross Unrealized Losses	(1,998)	(130)
Fair Value	130,799	124,241
Mortgage-backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	116,160	110,828
Gross Unrealized Gains	1,583	2,228
Gross Unrealized Losses	(1,380)
Fair Value	116,363	113,056
State and Local Governments [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	61,156	67,260
Gross Unrealized Gains	1,856	3,265
Gross Unrealized Losses	(525)	(10)
Fair Value	$ 62,487	$ 70,515

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).

+ References

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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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