ACQUISITIONS - Estimated fair value of assets acquired and liabilities (Details) - USD ($) $ in Thousands	6 Months Ended	12 Months Ended
	Jun. 30, 2023	Dec. 31, 2022	Mar. 01, 2023	Jun. 30, 2022	May 13, 2022
Consideration :
Cash	$ 6,376	$ 85,656
Recognized amounts of identifiable assets acquired and liabilities assumed:
Cash and cash equivalents	0	84,988
Investment securities	0	11,305
Loans, net of allowance for credit losses on PCD loans	0	436,796
Premises and equipment, net	58	11,317
Accrued interest and fees receivable	0	882
Other assets	2	30,337
Deposits	0	(522,295)
Other liabilities	(9)	(3,630)
Other Federal Home Loan Bank borrowings	0	(17,616)
Total identifiable assets, net	4,176	43,068
Goodwill	843,960	841,841		$ 849,813
Core Deposit Intangibles
Recognized amounts of identifiable assets acquired and liabilities assumed:
Deposits	0	7,970
Other Intangibles
Recognized amounts of identifiable assets acquired and liabilities assumed:
Other intangibles	4,125	3,014
Axiom
Consideration :
Cash	1,819
Recognized amounts of identifiable assets acquired and liabilities assumed:
Cash and cash equivalents	0
Investment securities	0
Loans, net of allowance for credit losses on PCD loans	0
Premises and equipment, net	25
Accrued interest and fees receivable	0
Other assets	2
Deposits	0
Other intangibles			$ 1,200
Other liabilities	(9)
Other Federal Home Loan Bank borrowings	0
Total identifiable assets, net	1,194
Goodwill	625		$ 600
Axiom | Core Deposit Intangibles
Recognized amounts of identifiable assets acquired and liabilities assumed:
Deposits	0
Axiom | Other Intangibles
Recognized amounts of identifiable assets acquired and liabilities assumed:
Other intangibles	1,176
Elmira acquisition
Consideration :
Cash		82,179
Recognized amounts of identifiable assets acquired and liabilities assumed:
Cash and cash equivalents		84,988
Investment securities		11,305			$ 11,300
Loans, net of allowance for credit losses on PCD loans		436,796			436,800
Premises and equipment, net		11,303
Accrued interest and fees receivable		882
Other assets		30,337
Deposits		(522,295)			(522,300)
Other liabilities		(3,596)
Other Federal Home Loan Bank borrowings		(17,616)
Total identifiable assets, net		40,074
Goodwill		42,105			42,100
Elmira acquisition | Core Deposit Intangibles
Recognized amounts of identifiable assets acquired and liabilities assumed:
Deposits		7,970			$ (8,000)
Elmira acquisition | Other Intangibles
Recognized amounts of identifiable assets acquired and liabilities assumed:
Other intangibles		0
Other
Consideration :
Cash	4,557	3,477
Recognized amounts of identifiable assets acquired and liabilities assumed:
Cash and cash equivalents	0	0
Investment securities	0	0
Loans, net of allowance for credit losses on PCD loans	0	0
Premises and equipment, net	33	14
Accrued interest and fees receivable	0	0
Other assets	0	0
Deposits	0	0
Other liabilities	0	(34)
Other Federal Home Loan Bank borrowings	0	0
Total identifiable assets, net	2,982	2,994
Goodwill	1,575	483
Other | Core Deposit Intangibles
Recognized amounts of identifiable assets acquired and liabilities assumed:
Deposits	0	0
Other | Other Intangibles
Recognized amounts of identifiable assets acquired and liabilities assumed:
Other intangibles	2,949	3,014
One Group Acquisitions
Recognized amounts of identifiable assets acquired and liabilities assumed:
Goodwill	$ 2,200	$ 42,588