Securities - Securities with Unrealized Losses Not Recognized in Income (Detail) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Schedule of Available-for-sale Securities [Line Items]
12 Months or less, Fair Value	$ 39,504	$ 302,275
12 Months or less, Unrealized Loss	(601)	(18,609)
More than 12 months, Fair Value	408,370	238,156
More than 12 months, Unrealized Loss	(57,078)	(49,159)
Total Fair Value	447,874	540,431
Total Unrealized Loss	(57,679)	(67,768)
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	224	21,042
12 Months or less, Unrealized Loss	(1)	(880)
More than 12 months, Fair Value	56,760	39,567
More than 12 months, Unrealized Loss	(4,074)	(4,606)
Total Fair Value	56,984	60,609
Total Unrealized Loss	(4,075)	(5,486)
Obligations of States and Political Subdivisions [Member]
Schedule of Available-for-sale Securities [Line Items]
12 Months or less, Fair Value	19,168	169,594
12 Months or less, Unrealized Loss	(78)	(13,016)
More than 12 months, Fair Value	162,291	73,967
More than 12 months, Unrealized Loss	(23,500)	(20,624)
Total Fair Value	181,459	243,561
Total Unrealized Loss	(23,578)	(33,640)
Mortgage-backed Securities in Government Sponsored Entities [Member]
Schedule of Available-for-sale Securities [Line Items]
12 Months or less, Fair Value	20,112	111,639
12 Months or less, Unrealized Loss	(522)	(4,713)
More than 12 months, Fair Value	189,319	124,622
More than 12 months, Unrealized Loss	(29,504)	(23,929)
Total Fair Value	209,431	236,261
Total Unrealized Loss	$ (30,026)	$ (28,642)