COMMITMENTS AND CONTINGENT LIABILITIES - Legal Proceeding and Other Contingent Liabilities (Details)														3 Months Ended
	Aug. 15, 2022 USD ($)	Jan. 20, 2022 USD ($)	Oct. 08, 2021 USD ($)	Oct. 08, 2020 USD ($)	Aug. 31, 2020 USD ($)	Aug. 14, 2020 claim	Jul. 16, 2020 USD ($)	May 01, 2020 USD ($)	Feb. 04, 2020 USD ($)	Jan. 10, 2020	Dec. 10, 2019 USD ($)	Nov. 26, 2019	Aug. 30, 2019 USD ($)	Sep. 30, 2022 USD ($)	Sep. 30, 2021 USD ($)	Sep. 30, 2020 USD ($)	Mar. 31, 2020 USD ($)	Jun. 30, 2019 USD ($)	May 14, 2021 USD ($)	Dec. 01, 2020 USD ($)	Apr. 30, 2020 USD ($)	Oct. 31, 2019 USD ($)
Commitments and Contingent Liabilities
Litigation-related expense														$ 0	$ 0
Deposit activity, the Bank's potential exposure for fraudulent activity														18,500,000
Amount set off																$ 16,000,000.0
Another bank returning/ calling back													$ 15,600,000
Lending activity, the Bank's potential exposure for fraudulent activity														15,800,000
Amount of commercial loan relationships with a customer for which the Bank is the originating lender and which there is potentially fraudulent activity														35,800,000
Non-interest expense associated with potentially fraudulent activity																2,500,000
Additional charges on non interest expense														0
Additional charge on provision for loan losses														0
Provision for loan losses related to charge-off the entire principal balance owed to the Bank related to the customer's commercial loan relationship as it relates to the potentially fraudulent activity																		$ 15,800,000
Partial recovery recognized related to the charge-off of the Mann Entities commercial loan relationships																$ 34,000	$ 1,700,000
Insurance recoveries related to partial reimbursement of defense costs														542,000	$ 1,100,000
Bank's Interest in cash and securities forfeited by Michael Mann, in which Bank filed petition to adjudicate the validity of the security interest in the forfeited property																			$ 14,900,000
Maximum potential monetary penalties related to investigation by the NYSDFS														30,000,000.0
Amount of potential monetary penalties related to damages sought by plaintiffs in the Southwestern, NatPay, DOJ and AHX proceedings														15,000,000.0
Southwestern Complaint
Commitments and Contingent Liabilities
Constructive trust, funds in question, per complaint																						$ 9,800,000
Number of days postponed in filing the answer										14 days		14 days
Amount of counterclaim/cross-claim damages sought by the Pioneer Parties								$ 15,600,000
Cachet Assertion
Commitments and Contingent Liabilities
Complaint, damages sought		$ 25,600,000
Alleged amount stolen per Cachet complaint		26,400,000
Portion of alleged stolen funds Bank is holding per assertion made by Cachet		8,500,000
Assertion made by a third party of the amount of actual damages		$ 8,500,000
Berkshire Bank Complaint
Commitments and Contingent Liabilities
Complaint, damages sought									$ 15,600,000
Number of cases dismissed | claim						5
Chemung Canal Trust Company Complaint
Commitments and Contingent Liabilities
Complaint, damages sought									$ 4,200,000
Number of cases dismissed | claim						3
Number of claims | claim						4
DOJ Complaint
Commitments and Contingent Liabilities
Value of funds in a third party account, claimed to be wrongfully seized by the Company and Bank to apply towards debts allegedly owed to the Bank																					$ 7,300,000
AXH Complaint
Commitments and Contingent Liabilities
Complaint, damages sought					$ 336,000
TBC Complaint
Commitments and Contingent Liabilities
Complaint, amount Bank seeks to recover																				$ 34,100,000
Minimum
Commitments and Contingent Liabilities
Loss contingency, estimate of possible loss														0
Minimum | Southwestern Complaint
Commitments and Contingent Liabilities
Complaint, damages sought											$ 9,800,000
Minimum | Southwestern Second Amended Complaint
Commitments and Contingent Liabilities
Complaint, damages sought							$ 9,800,000
Minimum | Southwestern Third Amended Complaint
Commitments and Contingent Liabilities
Complaint, damages sought				$ 39,000,000
Minimum | NatPay Complaint
Commitments and Contingent Liabilities
Complaint, damages sought											$ 4,000,000
Minimum | Natpay Amended Complaint
Commitments and Contingent Liabilities
Complaint, damages sought			$ 11,400,000
Minimum | Granite Solutions Groupe, Inc.
Commitments and Contingent Liabilities
Complaint, damages sought	$ 1,000,000
Maximum
Commitments and Contingent Liabilities
Loss contingency, estimate of possible loss														$ 51,300,000