ACQUISITIONS (Details) $ in Thousands						3 Months Ended		6 Months Ended		12 Months Ended
	May 13, 2022 USD ($)	Jan. 01, 2022 USD ($)	Aug. 02, 2021 USD ($)	Jul. 01, 2021 USD ($)	Jun. 01, 2021 USD ($)	Jun. 30, 2022 USD ($)	Jun. 30, 2021 USD ($)	Jun. 30, 2022 USD ($)	Jun. 30, 2021 USD ($)	Dec. 31, 2021 USD ($)
Acquisitions [Abstract]
Purchase price of acquisition								$ 84,643		$ 32,770
Deposits						$ 522,295		522,295		0
Loans						436,948		436,948		0
Provision for credit losses						6,038	$ (4,338)	6,944	$ (10,057)
Investment securities						11,305		11,305		0
Contingent consideration								0		2,900
Goodwill						849,813	794,892	849,813	794,892	799,109
Revenue earned						300		600
Direct expenses						100		200
Cash								(345)	2,900
Acquisition-related contingent consideration adjustment						400	0	400	0
Maximum
Acquisitions [Abstract]
Contingent consideration			$ 3,400
Core deposit intangibles
Acquisitions [Abstract]
Deposits						(7,970)		(7,970)		0
NuVantage Insurance, Inc. [Member]
Acquisitions [Abstract]
Intangibles					$ 1,400
Goodwill					1,400
Revenue earned						300		600
Direct expenses						300		600
Purchase price in cash					$ 2,900
NuVantage Insurance, Inc. [Member] | Maximum | Probability Adjusted Level Of Retained Revenue
Acquisitions [Abstract]
Contingent consideration, measurement input 2							5,400		5,400
NuVantage Insurance, Inc. [Member] | Minimum | Probability Adjusted Level Of Retained Revenue
Acquisitions [Abstract]
Contingent consideration, measurement input 2							$ 5,200		$ 5,200
Fringe Benefits Design of Minnesota, Inc ("FBD") [Member]
Acquisitions [Abstract]
Purchase price of acquisition										16,750
Deposits										0
Loans										0
Investment securities										0
Contingent consideration				$ 1,400						1,400
Goodwill				2,000						2,017
Revenue earned						1,000		2,500
Direct expenses						1,100		2,200
Cash				$ 15,400
Contingent consideration, measurement input				1.05			4.51		4.51
Period considered for additional consideration based on future retained revenue				2 years
Consideration payable term				3 years
Acquisition-related contingent consideration adjustment									$ 100
Fair value contingent consideration adjustment								1,500
Fringe Benefits Design of Minnesota, Inc ("FBD") [Member] | Maximum
Acquisitions [Abstract]
Contingent consideration				$ 2,700					2,700
Fringe Benefits Design of Minnesota, Inc ("FBD") [Member] | Maximum | Probability Adjusted Level Of Retained Revenue
Acquisitions [Abstract]
Contingent consideration, measurement input 2				5,800
Fringe Benefits Design of Minnesota, Inc ("FBD") [Member] | Minimum
Acquisitions [Abstract]
Contingent consideration				0					$ 0
Fringe Benefits Design of Minnesota, Inc ("FBD") [Member] | Minimum | Probability Adjusted Level Of Retained Revenue
Acquisitions [Abstract]
Contingent consideration, measurement input 2				5,600
Fringe Benefits Design of Minnesota, Inc ("FBD") [Member] | Customer Lists [Member]
Acquisitions [Abstract]
Intangibles				$ 14,000
Fringe Benefits Design of Minnesota, Inc ("FBD") [Member] | Core deposit intangibles
Acquisitions [Abstract]
Deposits										0
Thomas Gregory Associates [Member]
Acquisitions [Abstract]
Purchase price of acquisition		$ 2,500								13,120
Deposits										0
Loans										0
Investment securities										0
Contingent consideration			1,500							1,500
Intangibles		$ 2,500
Goodwill			2,200							$ 2,170
Revenue earned						500		2,000
Direct expenses						400		700
Cash			$ 11,600
Contingent consideration, measurement input 2						500		500
Period considered for additional consideration based on future retained revenue			3 years
Fair value contingent consideration adjustment								2,000
Thomas Gregory Associates [Member] | Within Two Years From Acquisition [Member]
Acquisitions [Abstract]
Consideration payable term			2 years
Thomas Gregory Associates [Member] | Within Three Years From Acquisition [Member]
Acquisitions [Abstract]
Consideration payable term			3 years
Thomas Gregory Associates [Member] | Maximum
Acquisitions [Abstract]
Contingent consideration								3,400
Contingent consideration, measurement input			1.09							4.55
Thomas Gregory Associates [Member] | Maximum | Probability Adjusted Level Of Retained Revenue
Acquisitions [Abstract]
Contingent consideration, measurement input 2			$ 3,800			$ 3,700		3,700
Thomas Gregory Associates [Member] | Minimum
Acquisitions [Abstract]
Contingent consideration			$ 0					$ 0
Contingent consideration, measurement input			0.82			4.44		4.44
Thomas Gregory Associates [Member] | Minimum | Probability Adjusted Level Of Retained Revenue
Acquisitions [Abstract]
Contingent consideration, measurement input 2			$ 2,300			$ 3,300		$ 3,300
Thomas Gregory Associates [Member] | Customer Lists [Member]
Acquisitions [Abstract]
Intangibles			$ 10,900
Thomas Gregory Associates [Member] | Core deposit intangibles
Acquisitions [Abstract]
Deposits										$ 0
Elmira Savings Bank [Member]
Acquisitions [Abstract]
Purchase price of acquisition								82,179
Assets acquired	$ 576,400
Deposits	522,300					522,295		522,295
Loans	437,000					436,948		436,948
Provision for credit losses	3,900					3,900		3,900
Investment securities	11,300					11,305		11,305
Contingent consideration								0
Goodwill	50,700					50,733		50,733
Revenue earned	2,400
Direct expenses	600
Elmira Savings Bank [Member] | Core deposit intangibles
Acquisitions [Abstract]
Deposits	$ 8,000					$ (7,970)		$ (7,970)