FAIR VALUE MEASUREMENTS, Key Methods and Assumptions Used (Details)	Sep. 30, 2021	Dec. 31, 2020
Collateral, Market, Income, Enterprise and Liquidation [Member] | Selling Costs [Member] | Minimum [Member]
Key methods and assumptions used in measuring fair value [Abstract]
Impaired loans, measurement input	0.06	0.06
Collateral, Market, Income, Enterprise and Liquidation [Member] | Selling Costs [Member] | Maximum [Member]
Key methods and assumptions used in measuring fair value [Abstract]
Impaired loans, measurement input	0.10	0.10
Discounted Cash Flows [Member] | Discount Rate Factor [Member]
Key methods and assumptions used in measuring fair value [Abstract]
Mortgage servicing rights, measurement input	0.0950	0.1000
Discounted Cash Flows [Member] | Constant Prepayment Rate [Member]
Key methods and assumptions used in measuring fair value [Abstract]
Mortgage servicing rights, measurement input	0.1795	0.2022