Securities - Gross Unrealized Losses and Fair Value, Aggregated by Investment Category (Detail) - USD ($) $ in Thousands	Jun. 30, 2024	Dec. 31, 2023
Schedule of Available-for-sale Securities [Line Items]
12 Months or less, Fair Value	$ 97,243	$ 39,504
12 Months or less, Unrealized Loss	(919)	(601)
More than 12 months, Fair Value	428,230	408,370
More than 12 months, Unrealized Loss	(63,575)	(57,078)
Total Fair Value	525,473	447,874
Total Unrealized Loss	(64,494)	(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	2,980	224
12 Months or less, Unrealized Loss	(8)	(1)
More than 12 months, Fair Value	56,087	56,760
More than 12 months, Unrealized Loss	(4,214)	(4,074)
Total Fair Value	59,067	56,984
Total Unrealized Loss	(4,222)	(4,075)
Obligations of States and Political Subdivisions [Member]
Schedule of Available-for-sale Securities [Line Items]
12 Months or less, Fair Value	93,938	19,168
12 Months or less, Unrealized Loss	(908)	(78)
More than 12 months, Fair Value	173,801	162,291
More than 12 months, Unrealized Loss	(26,970)	(23,500)
Total Fair Value	267,739	181,459
Total Unrealized Loss	(27,878)	(23,578)
Mortgage-backed Securities in Government Sponsored Entities [Member]
Schedule of Available-for-sale Securities [Line Items]
12 Months or less, Fair Value	325	20,112
12 Months or less, Unrealized Loss	(3)	(522)
More than 12 months, Fair Value	198,342	189,319
More than 12 months, Unrealized Loss	(32,391)	(29,504)
Total Fair Value	198,667	209,431
Total Unrealized Loss	$ (32,394)	$ (30,026)