FAIR VALUE MEASURES - Fair Value Measurements of Assets Measured at Fair Value on Non-Recurring Basis (Details) - Fair Value, Measurements, Nonrecurring - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Assets at fair value	$ 247,167	$ 239,859
Collateral-dependent loans
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Assets at fair value	58,580	98,426
Other real estate owned
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Assets at fair value	81	4,964
Mortgage servicing rights
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Assets at fair value	188,506	130,630
SBA servicing rights
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Assets at fair value		5,839
Level 1
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Assets at fair value	0	0
Level 1 | Collateral-dependent loans
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Assets at fair value	0	0
Level 1 | Other real estate owned
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Assets at fair value	0	0
Level 1 | Mortgage servicing rights
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Assets at fair value	0	0
Level 1 | SBA servicing rights
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Assets at fair value		0
Level 2
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Assets at fair value	0	5,839
Level 2 | Collateral-dependent loans
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Assets at fair value	0	0
Level 2 | Other real estate owned
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Assets at fair value	0	0
Level 2 | Mortgage servicing rights
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Assets at fair value	0	0
Level 2 | SBA servicing rights
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Assets at fair value		5,839
Level 3
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Assets at fair value	247,167	234,020
Level 3 | Collateral-dependent loans
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Assets at fair value	58,580	98,426
Level 3 | Other real estate owned
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Assets at fair value	81	4,964
Level 3 | Mortgage servicing rights
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Assets at fair value	$ 188,506	130,630
Level 3 | SBA servicing rights
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Assets at fair value		$ 0