FAIR VALUE - Unobservable Inputs Information (Details) - Mortgage servicing rights - Discounted cash flow - Unobservable inputs Level 3	Sep. 30, 2019	Dec. 31, 2018
Constant prepayment rate | Minimum
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Unobservable Input	0.080	0.070
Constant prepayment rate | Maximum
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Unobservable Input	0.277	0.204
Constant prepayment rate | Weighted Average
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Unobservable Input	0.151	0.101
Discount rate
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Unobservable Input	0.120	0.120
Discount rate | Weighted Average
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Unobservable Input	0.120	0.120