Investment Securities - Summary of Amortized Cost, Gross Unrealized Gains and Losses, and Fair Value of Investment Securities Available for Sale (Detail) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Debt Securities Available For Sale Reconciliation Of Fair Value To Amortized Cost [Line Items]
Amortized Cost	$ 119,828	$ 121,408
Gross Unrealized Gains	3,172	4,161
Gross Unrealized Losses	(252)	(122)
Fair Value	122,748	125,447
U.S. government agency securities [Member]
Debt Securities Available For Sale Reconciliation Of Fair Value To Amortized Cost [Line Items]
Amortized Cost	6,254
Gross Unrealized Gains	72
Fair Value	6,326
Small Business Administration Loan Pools [Member]
Debt Securities Available For Sale Reconciliation Of Fair Value To Amortized Cost [Line Items]
Amortized Cost	6,460	7,835
Gross Unrealized Gains	133	198
Gross Unrealized Losses	(39)	(39)
Fair Value	6,554	7,994
Obligations of state and political subdivisions [Member]
Debt Securities Available For Sale Reconciliation Of Fair Value To Amortized Cost [Line Items]
Amortized Cost	47,653	49,167
Gross Unrealized Gains	2,316	2,895
Gross Unrealized Losses	(51)	(3)
Fair Value	49,918	52,059
Mortgage-backed securities in government-sponsored entities [Member]
Debt Securities Available For Sale Reconciliation Of Fair Value To Amortized Cost [Line Items]
Amortized Cost	59,461	64,406
Gross Unrealized Gains	651	1,068
Gross Unrealized Losses	(162)	(80)
Fair Value	$ 59,950	$ 65,394

Debt securities available for sale reconciliation of fair value to amortized cost.

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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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