Securities - Gross Unrealized Losses, Aggregated by Investment Category and Length of Time (Detail) - USD ($) $ in Thousands	Sep. 30, 2024	Dec. 31, 2023
Schedule of Available-for-sale Securities [Line Items]
Gross Unrealized Losses, Less Than Twelve Months	$ (7)	$ (26)
Fair Value, Less Than Twelve Months	2,150	5,797
Gross Unrealized Losses, Twelve Months and Over	(25,164)	(36,835)
Fair Value, Twelve Months and Over	332,466	345,911
Gross Unrealized Losses, Total	(25,171)	(36,861)
Fair Value, Total	334,616	351,708
U.S. Treasury [Member]
Schedule of Available-for-sale Securities [Line Items]
Gross Unrealized Losses, Less Than Twelve Months	(1)	(4)
Fair Value, Less Than Twelve Months	248	494
Gross Unrealized Losses, Twelve Months and Over	(4,430)	(6,909)
Fair Value, Twelve Months and Over	72,558	79,528
Gross Unrealized Losses, Total	(4,431)	(6,913)
Fair Value, Total	72,806	80,022
U.S. Government Agencies [Member]
Schedule of Available-for-sale Securities [Line Items]
Gross Unrealized Losses, Twelve Months and Over	(8,372)	(12,738)
Fair Value, Twelve Months and Over	132,490	128,222
Gross Unrealized Losses, Total	(8,372)	(12,738)
Fair Value, Total	132,490	128,222
Mortgage-backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Gross Unrealized Losses, Less Than Twelve Months		(20)
Fair Value, Less Than Twelve Months		4,372
Gross Unrealized Losses, Twelve Months and Over	(9,083)	(11,909)
Fair Value, Twelve Months and Over	72,452	77,759
Gross Unrealized Losses, Total	(9,083)	(11,929)
Fair Value, Total	72,452	82,131
State and Local Governments [Member]
Schedule of Available-for-sale Securities [Line Items]
Gross Unrealized Losses, Less Than Twelve Months	(6)	(2)
Fair Value, Less Than Twelve Months	1,902	931
Gross Unrealized Losses, Twelve Months and Over	(3,279)	(5,279)
Fair Value, Twelve Months and Over	54,966	60,402
Gross Unrealized Losses, Total	(3,285)	(5,281)
Fair Value, Total	$ 56,868	$ 61,333