Fair Value of Assets and Liabilities - Assets and Liabilities Measured at Fair Value on Recurring Basis (Details) - USD ($)	Sep. 30, 2023	Dec. 31, 2022
Available-for-sale securities:
Total available-for-sale securities	$ 1,218,595,000	$ 1,218,985,000
Equity securities, at fair value	3,932,000	311,000
U.S. Treasury Securities and Obligations of U.S. Government Corporations and Agencies
Available-for-sale securities:
Total available-for-sale securities	211,929,000	220,527,000
Obligations of States and Political Subdivisions
Available-for-sale securities:
Total available-for-sale securities	266,473,000	287,698,000
Mortgage-backed Securities
Available-for-sale securities:
Total available-for-sale securities	672,522,000	627,880,000
Other Securities
Available-for-sale securities:
Total available-for-sale securities	67,671,000	82,880,000
Fair Value, Recurring
Available-for-sale securities:
Total available-for-sale securities	1,218,595,000	1,218,985,000
Equity securities, at fair value	3,932,000	311,000
Loans held for sale, fair value	6,233,000	338,000
Derivative assets: interest rate swaps	4,349,000	4,253,000
Total assets	1,233,109,000	1,223,887,000
Derivative liabilities: interest swaps	2,932,000	3,100,000
Fair Value, Recurring | U.S. Treasury Securities and Obligations of U.S. Government Corporations and Agencies
Available-for-sale securities:
Total available-for-sale securities	211,929,000	220,527,000
Fair Value, Recurring | Obligations of States and Political Subdivisions
Available-for-sale securities:
Total available-for-sale securities	266,473,000	287,698,000
Fair Value, Recurring | Mortgage-backed Securities
Available-for-sale securities:
Total available-for-sale securities	672,522,000	627,880,000
Fair Value, Recurring | Other Securities
Available-for-sale securities:
Total available-for-sale securities	67,671,000	82,880,000
Quoted Prices in Active Markets for Identical Assets (Level 1)
Available-for-sale securities:
Total available-for-sale securities	0	0
Equity securities, at fair value	3,932,000	311,000
Loans held for sale, fair value	0	0
Quoted Prices in Active Markets for Identical Assets (Level 1) | Fair Value, Recurring
Available-for-sale securities:
Total available-for-sale securities	0	0
Equity securities, at fair value	3,932,000	311,000
Loans held for sale, fair value	0	0
Derivative assets: interest rate swaps	0	0
Total assets	3,932,000	311,000
Derivative liabilities: interest swaps	0	0
Quoted Prices in Active Markets for Identical Assets (Level 1) | Fair Value, Recurring | U.S. Treasury Securities and Obligations of U.S. Government Corporations and Agencies
Available-for-sale securities:
Total available-for-sale securities	0	0
Quoted Prices in Active Markets for Identical Assets (Level 1) | Fair Value, Recurring | Obligations of States and Political Subdivisions
Available-for-sale securities:
Total available-for-sale securities	0	0
Quoted Prices in Active Markets for Identical Assets (Level 1) | Fair Value, Recurring | Mortgage-backed Securities
Available-for-sale securities:
Total available-for-sale securities	0	0
Quoted Prices in Active Markets for Identical Assets (Level 1) | Fair Value, Recurring | Other Securities
Available-for-sale securities:
Total available-for-sale securities	0	0
Significant Other Observable Inputs (Level 2)
Available-for-sale securities:
Total available-for-sale securities	1,212,835,000	1,209,736,000
Equity securities, at fair value	0	0
Loans held for sale, fair value	6,233,000	338,000
Significant Other Observable Inputs (Level 2) | Fair Value, Recurring
Available-for-sale securities:
Total available-for-sale securities	1,212,835,000	1,209,735,000
Equity securities, at fair value	0	0
Loans held for sale, fair value	6,233,000	338,000
Derivative assets: interest rate swaps	4,349,000	4,253,000
Total assets	1,223,417,000	1,214,326,000
Derivative liabilities: interest swaps	2,932,000	3,100,000
Significant Other Observable Inputs (Level 2) | Fair Value, Recurring | U.S. Treasury Securities and Obligations of U.S. Government Corporations and Agencies
Available-for-sale securities:
Total available-for-sale securities	211,929,000	220,527,000
Significant Other Observable Inputs (Level 2) | Fair Value, Recurring | Obligations of States and Political Subdivisions
Available-for-sale securities:
Total available-for-sale securities	266,473,000	287,698,000
Significant Other Observable Inputs (Level 2) | Fair Value, Recurring | Mortgage-backed Securities
Available-for-sale securities:
Total available-for-sale securities	672,522,000	627,880,000
Significant Other Observable Inputs (Level 2) | Fair Value, Recurring | Other Securities
Available-for-sale securities:
Total available-for-sale securities	61,911,000	73,630,000
Significant Unobservable Inputs (Level 3)
Available-for-sale securities:
Total available-for-sale securities	5,760,000	9,250,000
Equity securities, at fair value	0	0
Loans held for sale, fair value	0	0
Significant Unobservable Inputs (Level 3) | Fair Value, Recurring
Available-for-sale securities:
Total available-for-sale securities	5,760,000	9,250,000
Equity securities, at fair value	0	0
Loans held for sale, fair value	0	0
Derivative assets: interest rate swaps	0	0
Total assets	5,760,000	9,250,000
Derivative liabilities: interest swaps	0	0
Significant Unobservable Inputs (Level 3) | Fair Value, Recurring | U.S. Treasury Securities and Obligations of U.S. Government Corporations and Agencies
Available-for-sale securities:
Total available-for-sale securities	0	0
Significant Unobservable Inputs (Level 3) | Fair Value, Recurring | Obligations of States and Political Subdivisions
Available-for-sale securities:
Total available-for-sale securities	0	0
Significant Unobservable Inputs (Level 3) | Fair Value, Recurring | Mortgage-backed Securities
Available-for-sale securities:
Total available-for-sale securities	0	0
Significant Unobservable Inputs (Level 3) | Fair Value, Recurring | Other Securities
Available-for-sale securities:
Total available-for-sale securities	$ 5,760,000	$ 9,250,000