Fair Value Measurements - Assets and Liabilities Measured at Fair Value on Recurring Basis (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
ASSETS
Debt securities, available-for-sale, excluding accrued interest	$ 868,994	$ 770,393
Marketable equity securities	1,127	3,300
U.S. Treasury securities
ASSETS
Debt securities, available-for-sale, excluding accrued interest	85,300	10,282
Obligations of U.S. government corporations and agencies
ASSETS
Debt securities, available-for-sale, excluding accrued interest	71,205	82,904
Collateralized mortgage obligations of U.S. government corporations and agencies
ASSETS
Debt securities, available-for-sale, excluding accrued interest	208,985	209,296
Residential mortgage-backed securities of U.S. government corporations and agencies
ASSETS
Debt securities, available-for-sale, excluding accrued interest	60,442	67,778
Commercial mortgage-backed securities of U.S. government corporations and agencies
ASSETS
Debt securities, available-for-sale, excluding accrued interest	356,506	273,681
Obligations of states and political subdivisions
ASSETS
Debt securities, available-for-sale, excluding accrued interest	86,056	124,427
Fair Value Measurements, Recurring
ASSETS
Debt securities, available-for-sale, excluding accrued interest	868,994	770,393
Marketable equity securities	1,127	3,300
Total Securities	870,121	773,693
Securities held in a deferred compensation plan	9,320	6,794
Total Assets	922,531	861,706
LIABILITIES
Total Liabilities	42,554	79,418
Fair Value Measurements, Recurring | U.S. Treasury securities
ASSETS
Debt securities, available-for-sale, excluding accrued interest	85,300	10,282
Fair Value Measurements, Recurring | Obligations of U.S. government corporations and agencies
ASSETS
Debt securities, available-for-sale, excluding accrued interest	71,205	82,904
Fair Value Measurements, Recurring | Collateralized mortgage obligations of U.S. government corporations and agencies
ASSETS
Debt securities, available-for-sale, excluding accrued interest	208,985	209,296
Fair Value Measurements, Recurring | Residential mortgage-backed securities of U.S. government corporations and agencies
ASSETS
Debt securities, available-for-sale, excluding accrued interest	60,442	67,778
Fair Value Measurements, Recurring | Commercial mortgage-backed securities of U.S. government corporations and agencies
ASSETS
Debt securities, available-for-sale, excluding accrued interest	356,506	273,681
Fair Value Measurements, Recurring | Corporate obligations
ASSETS
Debt securities, available-for-sale, excluding accrued interest	500	2,025
Fair Value Measurements, Recurring | Obligations of states and political subdivisions
ASSETS
Debt securities, available-for-sale, excluding accrued interest	86,056	124,427
Fair Value Measurements, Recurring | Interest rate swaps
ASSETS
Derivative financial assets	42,177	78,319
LIABILITIES
Derivative financial liabilities	42,554	79,033
Fair Value Measurements, Recurring | Interest rate lock commitments
ASSETS
Derivative financial assets	812	2,900
Fair Value Measurements, Recurring | Forward sale contracts
ASSETS
Derivative financial assets	101
LIABILITIES
Derivative financial liabilities		385
Fair Value Measurements, Recurring | Level 1
ASSETS
Debt securities, available-for-sale, excluding accrued interest	85,300	10,282
Marketable equity securities	1,051	3,228
Total Securities	86,351	13,510
Securities held in a deferred compensation plan	9,320	6,794
Total Assets	95,671	20,304
LIABILITIES
Total Liabilities	0	0
Fair Value Measurements, Recurring | Level 1 | U.S. Treasury securities
ASSETS
Debt securities, available-for-sale, excluding accrued interest	85,300	10,282
Fair Value Measurements, Recurring | Level 1 | Obligations of U.S. government corporations and agencies
ASSETS
Debt securities, available-for-sale, excluding accrued interest	0	0
Fair Value Measurements, Recurring | Level 1 | Collateralized mortgage obligations of U.S. government corporations and agencies
ASSETS
Debt securities, available-for-sale, excluding accrued interest	0	0
Fair Value Measurements, Recurring | Level 1 | Residential mortgage-backed securities of U.S. government corporations and agencies
ASSETS
Debt securities, available-for-sale, excluding accrued interest	0	0
Fair Value Measurements, Recurring | Level 1 | Commercial mortgage-backed securities of U.S. government corporations and agencies
ASSETS
Debt securities, available-for-sale, excluding accrued interest	0	0
Fair Value Measurements, Recurring | Level 1 | Corporate obligations
ASSETS
Debt securities, available-for-sale, excluding accrued interest	0	0
Fair Value Measurements, Recurring | Level 1 | Obligations of states and political subdivisions
ASSETS
Debt securities, available-for-sale, excluding accrued interest	0	0
Fair Value Measurements, Recurring | Level 1 | Interest rate swaps
ASSETS
Derivative financial assets	0	0
LIABILITIES
Derivative financial liabilities	0	0
Fair Value Measurements, Recurring | Level 1 | Interest rate lock commitments
ASSETS
Derivative financial assets	0	0
Fair Value Measurements, Recurring | Level 1 | Forward sale contracts
ASSETS
Derivative financial assets	0
LIABILITIES
Derivative financial liabilities		0
Fair Value Measurements, Recurring | Level 2
ASSETS
Debt securities, available-for-sale, excluding accrued interest	783,694	760,111
Marketable equity securities	76	72
Total Securities	783,770	760,183
Securities held in a deferred compensation plan	0	0
Total Assets	825,947	838,502
LIABILITIES
Total Liabilities	42,554	79,418
Fair Value Measurements, Recurring | Level 2 | U.S. Treasury securities
ASSETS
Debt securities, available-for-sale, excluding accrued interest	0	0
Fair Value Measurements, Recurring | Level 2 | Obligations of U.S. government corporations and agencies
ASSETS
Debt securities, available-for-sale, excluding accrued interest	71,205	82,904
Fair Value Measurements, Recurring | Level 2 | Collateralized mortgage obligations of U.S. government corporations and agencies
ASSETS
Debt securities, available-for-sale, excluding accrued interest	208,985	209,296
Fair Value Measurements, Recurring | Level 2 | Residential mortgage-backed securities of U.S. government corporations and agencies
ASSETS
Debt securities, available-for-sale, excluding accrued interest	60,442	67,778
Fair Value Measurements, Recurring | Level 2 | Commercial mortgage-backed securities of U.S. government corporations and agencies
ASSETS
Debt securities, available-for-sale, excluding accrued interest	356,506	273,681
Fair Value Measurements, Recurring | Level 2 | Corporate obligations
ASSETS
Debt securities, available-for-sale, excluding accrued interest	500	2,025
Fair Value Measurements, Recurring | Level 2 | Obligations of states and political subdivisions
ASSETS
Debt securities, available-for-sale, excluding accrued interest	86,056	124,427
Fair Value Measurements, Recurring | Level 2 | Interest rate swaps
ASSETS
Derivative financial assets	42,177	78,319
LIABILITIES
Derivative financial liabilities	42,554	79,033
Fair Value Measurements, Recurring | Level 2 | Interest rate lock commitments
ASSETS
Derivative financial assets	0	0
Fair Value Measurements, Recurring | Level 2 | Forward sale contracts
ASSETS
Derivative financial assets	0
LIABILITIES
Derivative financial liabilities		385
Fair Value Measurements, Recurring | Level 3
ASSETS
Debt securities, available-for-sale, excluding accrued interest	0	0
Marketable equity securities	0	0
Total Securities	0	0
Securities held in a deferred compensation plan	0	0
Total Assets	913	2,900
LIABILITIES
Total Liabilities	0	0
Fair Value Measurements, Recurring | Level 3 | U.S. Treasury securities
ASSETS
Debt securities, available-for-sale, excluding accrued interest	0	0
Fair Value Measurements, Recurring | Level 3 | Obligations of U.S. government corporations and agencies
ASSETS
Debt securities, available-for-sale, excluding accrued interest	0	0
Fair Value Measurements, Recurring | Level 3 | Collateralized mortgage obligations of U.S. government corporations and agencies
ASSETS
Debt securities, available-for-sale, excluding accrued interest	0	0
Fair Value Measurements, Recurring | Level 3 | Residential mortgage-backed securities of U.S. government corporations and agencies
ASSETS
Debt securities, available-for-sale, excluding accrued interest	0	0
Fair Value Measurements, Recurring | Level 3 | Commercial mortgage-backed securities of U.S. government corporations and agencies
ASSETS
Debt securities, available-for-sale, excluding accrued interest	0	0
Fair Value Measurements, Recurring | Level 3 | Corporate obligations
ASSETS
Debt securities, available-for-sale, excluding accrued interest	0	0
Fair Value Measurements, Recurring | Level 3 | Obligations of states and political subdivisions
ASSETS
Debt securities, available-for-sale, excluding accrued interest	0	0
Fair Value Measurements, Recurring | Level 3 | Interest rate swaps
ASSETS
Derivative financial assets	0	0
LIABILITIES
Derivative financial liabilities	0	0
Fair Value Measurements, Recurring | Level 3 | Interest rate lock commitments
ASSETS
Derivative financial assets	812	2,900
Fair Value Measurements, Recurring | Level 3 | Forward sale contracts
ASSETS
Derivative financial assets	$ 101
LIABILITIES
Derivative financial liabilities		$ 0