Securities - Gross Unrealized Losses and Fair Value, Aggregated by Investment Category (Detail) - USD ($) $ in Thousands	Mar. 31, 2024	Dec. 31, 2023
Schedule of Available-for-sale Securities [Line Items]
12 Months or less, Fair Value	$ 50,921	$ 39,504
12 Months or less, Unrealized Loss	(340)	(601)
More than 12 months, Fair Value	429,236	408,370
More than 12 months, Unrealized Loss	(63,950)	(57,078)
Total Fair Value	480,157	447,874
Total Unrealized Loss	(64,290)	(57,679)
U.S. Treasury Securities and Obligations of U.S. Government Agencies [Member]
Schedule of Available-for-sale Securities [Line Items]
12 Months or less, Fair Value	2,102	224
12 Months or less, Unrealized Loss	(5)	(1)
More than 12 months, Fair Value	56,010	56,760
More than 12 months, Unrealized Loss	(4,433)	(4,074)
Total Fair Value	58,112	56,984
Total Unrealized Loss	(4,438)	(4,075)
Obligations of States and Political Subdivisions [Member]
Schedule of Available-for-sale Securities [Line Items]
12 Months or less, Fair Value	48,073	19,168
12 Months or less, Unrealized Loss	(323)	(78)
More than 12 months, Fair Value	171,551	162,291
More than 12 months, Unrealized Loss	(26,329)	(23,500)
Total Fair Value	219,624	181,459
Total Unrealized Loss	(26,652)	(23,578)
Mortgage-backed Securities in Government Sponsored Entities [Member]
Schedule of Available-for-sale Securities [Line Items]
12 Months or less, Fair Value	746	20,112
12 Months or less, Unrealized Loss	(12)	(522)
More than 12 months, Fair Value	201,675	189,319
More than 12 months, Unrealized Loss	(33,188)	(29,504)
Total Fair Value	202,421	209,431
Total Unrealized Loss	$ (33,200)	$ (30,026)