Investment Securities - Summary of Amortized Cost and Held-to-maturity, Gross Unrealized Gains and Losses, and Fair Value of Investment Securities Available for Sale (Detail) - USD ($)	Mar. 31, 2024	Dec. 31, 2023	Mar. 31, 2023	Dec. 31, 2022
Debt Securities Available For Sale Reconciliation Of Fair Value To Amortized Cost [Line Items]
Amortized Cost	$ 140,442,000	$ 120,372,000
Gross Unrealized Gains	336,000	1,280,000
Gross Unrealized Losses	(6,829,000)	(6,162,000)
Allowance for Credit Losses	0	0
Fair Value	133,949,000	115,490,000
Held-to-Maturity, Amortized Cost	36,616,000	36,735,000
Gross Unrecognized Gain	0	0
Gross Unrecognized Losses	(2,347,000)	(2,499,000)
Held-to-maturity, Fair value	34,269,000	34,236,000
Allowance for Credit Losses	(507,000)	(512,000)
US Government Agency securities [Member]
Debt Securities Available For Sale Reconciliation Of Fair Value To Amortized Cost [Line Items]
Amortized Cost	12,743,000	12,711,000
Gross Unrealized Gains	106,000	279,000
Gross Unrealized Losses	0	(5,000)
Allowance for Credit Losses	0	0
Fair Value	12,849,000	12,985,000
US Government Treasury securities [Member]
Debt Securities Available For Sale Reconciliation Of Fair Value To Amortized Cost [Line Items]
Amortized Cost	4,942,000	4,925,000
Gross Unrealized Gains	2,000	17,000
Gross Unrealized Losses	0	0
Allowance for Credit Losses	0	0
Fair Value	4,944,000	4,942,000
Obligations of state and political subdivisions [Member]
Debt Securities Available For Sale Reconciliation Of Fair Value To Amortized Cost [Line Items]
Amortized Cost	49,231,000	49,640,000
Gross Unrealized Gains	55,000	420,000
Gross Unrealized Losses	(3,319,000)	(3,015,000)
Allowance for Credit Losses	0	0
Fair Value	45,967,000	47,045,000
Mortgage-backed securities in government-sponsored entities [Member]
Debt Securities Available For Sale Reconciliation Of Fair Value To Amortized Cost [Line Items]
Amortized Cost	71,276,000	50,795,000
Gross Unrealized Gains	173,000	515,000
Gross Unrealized Losses	(3,489,000)	(3,129,000)
Allowance for Credit Losses	0	0
Fair Value	67,960,000	48,181,000
Other securities [Member]
Debt Securities Available For Sale Reconciliation Of Fair Value To Amortized Cost [Line Items]
Amortized Cost	2,250,000	2,301,000
Gross Unrealized Gains	0	49,000
Gross Unrealized Losses	(21,000)	(13,000)
Allowance for Credit Losses	0	0
Fair Value	2,229,000	2,337,000
Corporate Debentures [Member]
Debt Securities Available For Sale Reconciliation Of Fair Value To Amortized Cost [Line Items]
Held-to-Maturity, Amortized Cost	15,000,000	15,000,000
Gross Unrecognized Gain	0	0
Gross Unrecognized Losses	(1,455,000)	(1,592,000)
Held-to-maturity, Fair value	13,545,000	13,408,000
Allowance for Credit Losses	(507,000)	(512,000)	$ (533,000)	$ 0
Structured Mortgage-backed Securities [Member]
Debt Securities Available For Sale Reconciliation Of Fair Value To Amortized Cost [Line Items]
Held-to-Maturity, Amortized Cost	21,616,000	21,735,000
Gross Unrecognized Gain	0	0
Gross Unrecognized Losses	(892,000)	(907,000)
Held-to-maturity, Fair value	20,724,000	20,828,000
Allowance for Credit Losses	$ 0	$ 0