Securities - Available for Sale Securities (Detail) - USD ($) $ in Thousands	Mar. 31, 2024	Dec. 31, 2023
Debt Securities, Available-for-Sale [Line Items]
Amortized Cost, Total securities available for sale	$ 668,764	$ 672,892
Gross Unrealized Gains	1,775	3,059
Gross Unrealized Losses	(64,290)	(57,679)
Fair Value	606,249	618,272
U.S. Treasury Securities and Obligations of U.S. Government Agencies [Member]
Debt Securities, Available-for-Sale [Line Items]
Amortized Cost, Total securities available for sale	72,013	71,418
Gross Unrealized Gains	467	315
Gross Unrealized Losses	(4,438)	(4,075)
Fair Value	68,042	67,658
Obligations of States and Political Subdivisions [Member]
Debt Securities, Available-for-Sale [Line Items]
Amortized Cost, Total securities available for sale	358,809	359,452
Gross Unrealized Gains	1,294	2,725
Gross Unrealized Losses	(26,652)	(23,578)
Fair Value	333,451	338,599
Mortgage-backed Securities in Government Sponsored Entities [Member]
Debt Securities, Available-for-Sale [Line Items]
Amortized Cost, Total securities available for sale	237,942	242,022
Gross Unrealized Gains	14	19
Gross Unrealized Losses	(33,200)	(30,026)
Fair Value	$ 204,756	$ 212,015