Securities - Available for Sale Securities (Detail) - USD ($) $ in Thousands	Sep. 30, 2023	Dec. 31, 2022
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost, Total securities available for sale	$ 687,603	$ 682,351
Gross Unrealized Gains	242	819
Gross Unrealized Losses	(94,358)	(67,768)
Fair Value	593,487	615,402
U.S. Treasury Securities and Obligations of U.S. Government Agencies [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost, Total securities available for sale	77,081	66,495
Gross Unrealized Gains	192	20
Gross Unrealized Losses	(5,978)	(5,486)
Fair Value	71,295	61,029
Obligations of States and Political Subdivisions [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost, Total securities available for sale	360,019	350,104
Gross Unrealized Gains	45	784
Gross Unrealized Losses	(49,529)	(33,640)
Fair Value	310,535	317,248
Mortgage-backed Securities in Government Sponsored Entities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost, Total securities available for sale	250,503	265,752
Gross Unrealized Gains	5	15
Gross Unrealized Losses	(38,851)	(28,642)
Fair Value	$ 211,657	$ 237,125