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ACQUISITIONS (Details) $ in Thousands				12 Months Ended
	Feb. 01, 2024 USD ($) loan	Mar. 01, 2023 USD ($)	May 13, 2022 USD ($) item	Dec. 31, 2024 USD ($)	Dec. 31, 2023 USD ($)	Dec. 31, 2022 USD ($)	Sep. 30, 2024 USD ($)
Acquisitions
Number of installments of contingent consideration payments | loan	4
Goodwill				$ 853,225	$ 845,396	$ 841,841
Revenue				746,303	652,119	679,355
Maximum estimated amount	$ 1,500
Carrying value of other intangibles				100
Net assets				200
New York Based Insurance Agency
Acquisitions
Maximum contingent consideration liability that could be paid	4,500
Business combination, net assets	4,400
Fair value of the contingent consideration	5,500
Certain assets of creative plan design limited
Acquisitions
Purchase price of acquisition				8,927
Purchase price in cash	5,900
Aggregate consideration in contingent consideration arrangements	$ 3,000
Term of revenue target for contingent consideration arrangements	3 years
Minimum contingent consideration liability that could be paid	$ 0
Maximum contingent consideration liability that could be paid	2,000
Business combination, net assets				4,542
Fair value of the contingent consideration	$ 3,000
Contingent consideration				3,066
Goodwill				4,385
Loans				0
Investment securities				0
Deposits				0
Certain assets of creative plan design limited | Core deposit intangibles
Acquisitions
Deposits				0
Certain assets of creative plan design limited | Other Intangible Assets
Acquisitions
Other intangibles				5,500
Certain assets of creative plan design limited | Measurement input discount rate | Fair Value, Inputs, Level 3 [Member]
Acquisitions
Contingent consideration, measurement input	82
Certain assets of creative plan design limited | Measurement input discount rate | Minimum | Fair Value, Inputs, Level 3 [Member]
Acquisitions
Contingent consideration, measurement input	15.1
Certain assets of creative plan design limited | Measurement input discount rate | Maximum | Fair Value, Inputs, Level 3 [Member]
Acquisitions
Contingent consideration, measurement input	19.1
Certain assets of financial service companies
Acquisitions
Purchase price of acquisition					8,200
Purchase price in cash					6,800
Aggregate consideration in contingent consideration arrangements					1,400
Assets acquired					5,200
Goodwill					$ 3,000
Certain assets of financial service companies | Minimum
Acquisitions
Term of revenue target for contingent consideration arrangements					2 years
Certain assets of financial service companies | Maximum
Acquisitions
Term of revenue target for contingent consideration arrangements					5 years
Certain assets of financial service companies | Customer list intangible
Acquisitions
Other intangibles					$ 5,000
Axiom
Acquisitions
Purchase price of acquisition					1,819
Purchase price in cash		$ 1,800
Business combination, net assets					1,194
Contingent consideration					0
Other intangibles		1,200
Goodwill		$ 600			625
Revenue				1,900	800
Direct expenses				1,900	1,800
Loans					0
Investment securities					0
Deposits					0
Axiom | Core deposit intangibles
Acquisitions
Deposits					0
Axiom | Other Intangible Assets
Acquisitions
Other intangibles					1,176
Thomas Gregory Associates Insurance Brokers, Inc.
Acquisitions
Fair value of the contingent consideration							$ 800
Elmira Savings Bank
Acquisitions
Purchase price of acquisition			$ 82,200
Assets acquired			583,600
Goodwill			$ 42,100
Revenue				14,900	12,100
Direct expenses				4,900	3,100
Number of county | item			5
Loans			$ 436,800
Investment securities			11,300
Deposits			522,300
Increase (decrease) in other liabilities as a result of reclassification and adjustment					$ (100)
Elmira Savings Bank | Core deposit intangibles
Acquisitions
Deposits			$ 8,000
OneGroup
Acquisitions
Purchase price of acquisition						3,500
Goodwill						500
OneGroup | Customer list intangible
Acquisitions
Other intangibles						2,900
OneGroup | Other Intangible Assets
Acquisitions
Other intangibles						$ 100
Certain assets of New York and Florida based insurance agency
Acquisitions
Purchase price in cash				$ 9,600
Term of revenue target for contingent consideration arrangements				2 years
Maximum contingent consideration liability that could be paid				$ 1,400
Business combination, net assets				6,400
Fair value of the contingent consideration				700
Other intangibles				6,800
Goodwill				$ 3,900

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