Fair Value Measurements - Assets and Liabilities Measured at Fair Value on Recurring Basis (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
ASSETS
Debt securities available-for-sale	$ 813,883	$ 770,393
Marketable equity securities	3,416	3,300
U.S. Treasury securities
ASSETS
Debt securities available-for-sale	63,268	10,282
Obligations of U.S. government corporations and agencies
ASSETS
Debt securities available-for-sale	82,028	82,904
Collateralized mortgage obligations of U.S. government corporations and agencies
ASSETS
Debt securities available-for-sale	217,916	209,296
Residential mortgage-backed securities of U.S. government corporations and agencies
ASSETS
Debt securities available-for-sale	63,911	67,778
Commercial mortgage-backed securities of U.S. government corporations and agencies
ASSETS
Debt securities available-for-sale	277,253	273,681
Obligations of states and political subdivisions
ASSETS
Debt securities available-for-sale	107,505	124,427
Fair Value Measurements, Recurring
ASSETS
Debt securities available-for-sale	813,883	770,393
Marketable equity securities	3,416	3,300
Total Securities	817,299	773,693
Securities held in a deferred compensation plan	7,178	6,794
Total Assets	866,627	861,706
LIABILITIES
Total Liabilities	40,818	79,418
Fair Value Measurements, Recurring \| U.S. Treasury securities
ASSETS
Debt securities available-for-sale	63,268	10,282
Fair Value Measurements, Recurring \| Obligations of U.S. government corporations and agencies
ASSETS
Debt securities available-for-sale	82,028	82,904
Fair Value Measurements, Recurring \| Collateralized mortgage obligations of U.S. government corporations and agencies
ASSETS
Debt securities available-for-sale	217,916	209,296
Fair Value Measurements, Recurring \| Residential mortgage-backed securities of U.S. government corporations and agencies
ASSETS
Debt securities available-for-sale	63,911	67,778
Fair Value Measurements, Recurring \| Commercial mortgage-backed securities of U.S. government corporations and agencies
ASSETS
Debt securities available-for-sale	277,253	273,681
Fair Value Measurements, Recurring \| Corporate obligations
ASSETS
Debt securities available-for-sale	2,002	2,025
Fair Value Measurements, Recurring \| Obligations of states and political subdivisions
ASSETS
Debt securities available-for-sale	107,505	124,427
Fair Value Measurements, Recurring \| Interest rate swaps
ASSETS
Derivative financial assets	40,415	78,319
LIABILITIES
Derivative financial liabilities	40,818	79,033
Fair Value Measurements, Recurring \| Interest rate lock commitments
ASSETS
Derivative financial assets	1,509	2,900
Fair Value Measurements, Recurring \| Forward sale contracts
ASSETS
Derivative financial assets		226
LIABILITIES
Derivative financial liabilities		385
Fair Value Measurements, Recurring \| Level 1
ASSETS
Debt securities available-for-sale	0	0
Marketable equity securities	3,328	3,228
Total Securities	3,328	3,228
Securities held in a deferred compensation plan	7,178	6,794
Total Assets	10,506	10,022
LIABILITIES
Total Liabilities	0	0
Fair Value Measurements, Recurring \| Level 1 \| U.S. Treasury securities
ASSETS
Debt securities available-for-sale	0	0
Fair Value Measurements, Recurring \| Level 1 \| Obligations of U.S. government corporations and agencies
ASSETS
Debt securities available-for-sale	0	0
Fair Value Measurements, Recurring \| Level 1 \| Collateralized mortgage obligations of U.S. government corporations and agencies
ASSETS
Debt securities available-for-sale	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	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	0	0
Fair Value Measurements, Recurring \| Level 1 \| Corporate obligations
ASSETS
Debt securities available-for-sale	0	0
Fair Value Measurements, Recurring \| Level 1 \| Obligations of states and political subdivisions
ASSETS
Debt securities available-for-sale	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	813,883	770,393
Marketable equity securities	88	72
Total Securities	813,971	770,465
Securities held in a deferred compensation plan	0	0
Total Assets	854,386	848,784
LIABILITIES
Total Liabilities	40,818	79,418
Fair Value Measurements, Recurring \| Level 2 \| U.S. Treasury securities
ASSETS
Debt securities available-for-sale	63,268	10,282
Fair Value Measurements, Recurring \| Level 2 \| Obligations of U.S. government corporations and agencies
ASSETS
Debt securities available-for-sale	82,028	82,904
Fair Value Measurements, Recurring \| Level 2 \| Collateralized mortgage obligations of U.S. government corporations and agencies
ASSETS
Debt securities available-for-sale	217,916	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	63,911	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	277,253	273,681
Fair Value Measurements, Recurring \| Level 2 \| Corporate obligations
ASSETS
Debt securities available-for-sale	2,002	2,025
Fair Value Measurements, Recurring \| Level 2 \| Obligations of states and political subdivisions
ASSETS
Debt securities available-for-sale	107,505	124,427
Fair Value Measurements, Recurring \| Level 2 \| Interest rate swaps
ASSETS
Derivative financial assets	40,415	78,319
LIABILITIES
Derivative financial liabilities	40,818	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	0	0
Marketable equity securities	0	0
Total Securities	0	0
Securities held in a deferred compensation plan	0	0
Total Assets	1,735	2,900
LIABILITIES
Total Liabilities	0	0
Fair Value Measurements, Recurring \| Level 3 \| U.S. Treasury securities
ASSETS
Debt securities available-for-sale	0	0
Fair Value Measurements, Recurring \| Level 3 \| Obligations of U.S. government corporations and agencies
ASSETS
Debt securities available-for-sale	0	0
Fair Value Measurements, Recurring \| Level 3 \| Collateralized mortgage obligations of U.S. government corporations and agencies
ASSETS
Debt securities available-for-sale	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	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	0	0
Fair Value Measurements, Recurring \| Level 3 \| Corporate obligations
ASSETS
Debt securities available-for-sale	0	0
Fair Value Measurements, Recurring \| Level 3 \| Obligations of states and political subdivisions
ASSETS
Debt securities available-for-sale	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	$ 1,509	2,900
Fair Value Measurements, Recurring \| Level 3 \| Forward sale contracts
ASSETS
Derivative financial assets		226
LIABILITIES
Derivative financial liabilities		$ 0

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Fair value portion of probable future economic benefits obtained or controlled by an entity as a result of past transactions or events.

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Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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