FAIR VALUE MEASUREMENTS - Valuation assumptions (Details) - Fair Value Measurement Level 3 $ in Millions	Dec. 31, 2022 USD ($)	Dec. 31, 2021 USD ($)
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Impaired loans	$ 47.2	$ 61.6
Reserves related to impaired loans	$ 0.0	$ 0.0
Prepayment Rate | Minimum
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Alternative investment measurement input	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	0.45
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	0.077
Discount Rate | Maximum
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Alternative investment measurement input	0.100