FAIR VALUE MEASUREMENTS - Valuation assumptions (Details) - Fair Value Measurement Level 3 $ in Millions	Mar. 31, 2023 USD ($)	Dec. 31, 2022 USD ($)
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Impaired loans	$ 37.5	$ 47.2
Prepayment Rate | Minimum
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Alternative investment measurement input	0.35	0.35
Prepayment Rate | Minimum | Mortgage Servicing Rights.
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Alternative investment measurement input	0.20
Prepayment Rate | Maximum
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Alternative investment measurement input	0.34	0.34
Prepayment Rate | Maximum | Mortgage Servicing Rights.
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Alternative investment measurement input	0.30
Discount Rate | Mortgage Servicing Rights.
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Alternative investment measurement input	0.10
Discount Rate | Minimum
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Alternative investment measurement input	0.0892	0.0892
Discount Rate | Maximum
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Alternative investment measurement input	0.100	0.100