Fair Value of Assets and Liabilities - Assets and Liabilities Measured at Fair Value on Recurring Basis (Details) - USD ($)	Mar. 31, 2022	Dec. 31, 2021
Available-for-sale securities:
Total available-for-sale securities	$ 1,466,950,000	$ 1,421,422,000
Equity securities, at fair value	369,000	397,000
U.S. Treasury Securities and Obligations of U.S. Government Corporations and Agencies
Available-for-sale securities:
Total available-for-sale securities	247,976,000	203,815,000
Obligations of States and Political Subdivisions
Available-for-sale securities:
Total available-for-sale securities	358,679,000	395,457,000
Mortgage-backed Securities
Available-for-sale securities:
Total available-for-sale securities	761,527,000	791,038,000
Other Securities
Available-for-sale securities:
Total available-for-sale securities	98,768,000	31,112,000
Fair Value, Recurring
Available-for-sale securities:
Total available-for-sale securities	1,466,950,000	1,421,422,000
Equity securities, at fair value	369,000	397,000
Derivative assets, Interest rate swaps	2,286,000	809,000
Total assets	1,469,605,000	1,422,628,000
Derivative liabilities, Interest rate swaps	2,167,000	1,476,000
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	247,976,000	203,815,000
Fair Value, Recurring | Obligations of States and Political Subdivisions
Available-for-sale securities:
Total available-for-sale securities	358,679,000	395,457,000
Fair Value, Recurring | Mortgage-backed Securities
Available-for-sale securities:
Total available-for-sale securities	761,527,000	791,038,000
Fair Value, Recurring | Other Securities
Available-for-sale securities:
Total available-for-sale securities	98,768,000	31,112,000
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	369,000	397,000
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	369,000	397,000
Derivative assets, Interest rate swaps	0	0
Total assets	369,000	397,000
Derivative liabilities, Interest rate 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	1,466,950,000	1,421,323,000
Equity securities, at fair value	0	0
Significant Other Observable Inputs (Level 2) | Fair Value, Recurring
Available-for-sale securities:
Total available-for-sale securities	1,466,950,000	1,421,323,000
Equity securities, at fair value	0	0
Derivative assets, Interest rate swaps	2,286,000	809,000
Total assets	1,469,236,000	1,422,132,000
Derivative liabilities, Interest rate swaps	2,167,000	1,476,000
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	247,976,000	203,815,000
Significant Other Observable Inputs (Level 2) | Fair Value, Recurring | Obligations of States and Political Subdivisions
Available-for-sale securities:
Total available-for-sale securities	358,679,000	395,358,000
Significant Other Observable Inputs (Level 2) | Fair Value, Recurring | Mortgage-backed Securities
Available-for-sale securities:
Total available-for-sale securities	761,527,000	791,038,000
Significant Other Observable Inputs (Level 2) | Fair Value, Recurring | Other Securities
Available-for-sale securities:
Total available-for-sale securities	98,768,000	31,112,000
Significant Unobservable Inputs (Level 3)
Available-for-sale securities:
Total available-for-sale securities	0	99,000
Equity securities, at fair value	0	0
Significant Unobservable Inputs (Level 3) | Fair Value, Recurring
Available-for-sale securities:
Total available-for-sale securities	0	99,000
Equity securities, at fair value	0	0
Derivative assets, Interest rate swaps	0	0
Total assets	0	99,000
Derivative liabilities, Interest rate 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	99,000
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	$ 0	$ 0