NATURE OF BUSINESS AND SIGNIFICANT ACCOUNTING POLICIES - Estimated useful lives of premises and equipment (Details)	12 Months Ended
	Dec. 31, 2021
Minimum | Building and improvements
Property, Plant and Equipment [Line Items]
Estimated useful lives of new premises and equipment	25 years
Minimum | Leasehold improvements
Property, Plant and Equipment [Line Items]
Estimated useful lives of new premises and equipment	5 years
Minimum | Furniture and equipment
Property, Plant and Equipment [Line Items]
Estimated useful lives of new premises and equipment	3 years
Maximum | Building and improvements
Property, Plant and Equipment [Line Items]
Estimated useful lives of new premises and equipment	40 years
Maximum | Leasehold improvements
Property, Plant and Equipment [Line Items]
Estimated useful lives of new premises and equipment	15 years
Maximum | Furniture and equipment
Property, Plant and Equipment [Line Items]
Estimated useful lives of new premises and equipment	10 years