LOAN SERVICING RIGHTS - Narrative (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Contractually Specified Servicing Fees, Late Fees, and Ancillary Fees Earned in Exchange for Servicing Financial Assets [Line Items]
Servicing fees	$ 37.2	$ 19.9	$ 4.5
Residential mortgage
Contractually Specified Servicing Fees, Late Fees, and Ancillary Fees Earned in Exchange for Servicing Financial Assets [Line Items]
Servicing fees	31.1	14.0	2.4
SBA
Contractually Specified Servicing Fees, Late Fees, and Ancillary Fees Earned in Exchange for Servicing Financial Assets [Line Items]
Servicing fees	4.4	3.6	2.1
Indirect automobile
Contractually Specified Servicing Fees, Late Fees, and Ancillary Fees Earned in Exchange for Servicing Financial Assets [Line Items]
Servicing fees	$ 1.7	$ 2.3	$ 0.0