LOANS AND ALLOWANCE FOR CREDIT LOSSES - Collateral Dependent (Details) - USD ($) $ in Thousands	Sep. 30, 2023		Jun. 30, 2023	Dec. 31, 2022		Sep. 30, 2022	Jun. 30, 2022	Dec. 31, 2021
Financing Receivable, Allowance for Credit Loss [Line Items]
Amortized Cost Basis	$ 4,999			$ 7,482
Related Allowance	20,252	[1]	$ 20,172	19,659	[1]	$ 18,631	$ 17,485	$ 21,025
Commercial and Agricultural
Financing Receivable, Allowance for Credit Loss [Line Items]
Amortized Cost Basis	1,174			2,112
Related Allowance	4,146		4,121	3,373		3,515	3,564	3,591
Commercial Mortgages
Financing Receivable, Allowance for Credit Loss [Line Items]
Amortized Cost Basis	3,825			4,383
Related Allowance	11,025		$ 10,994	$ 11,576		$ 10,986	$ 10,314	$ 13,556
Collateral Pledged
Financing Receivable, Allowance for Credit Loss [Line Items]
Amortized Cost Basis	4,133
Related Allowance	241
Commercial Real Estate And Business Assets | Commercial and Agricultural | Commercial and industrial
Financing Receivable, Allowance for Credit Loss [Line Items]
Amortized Cost Basis	286
Related Allowance	211
Commercial Real Estate and Residential Real Estate | Commercial Mortgages | Commercial mortgages, other
Financing Receivable, Allowance for Credit Loss [Line Items]
Amortized Cost Basis	3,847
Related Allowance	$ 30

[1] Effective January 1, 2023, the allowance calculation is based upon Current Expected Credit loss methodology. Prior to January 1, 2023, the allowance calculation was based upon incurred loss methodology. Refer to Note 1 for further discussion.