REVENUES - Disaggregation of Revenue (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2022 USD ($) segment	Mar. 31, 2021 USD ($) segment
Revenue from Contract with Customer [Abstract]
Number of reportable segments | segment	1	1
Disaggregation of Revenue [Line Items]
Total revenues	$ 25,047	$ 24,202
Interchange and card revenue
Disaggregation of Revenue [Line Items]
Total revenues	6,643	8,244
Servicing fees from Partner Bank
Disaggregation of Revenue [Line Items]
Total revenues	14,192	9,372
Account fees
Disaggregation of Revenue [Line Items]
Total revenues	2,555	2,661
University fees
Disaggregation of Revenue [Line Items]
Total revenues	1,603	1,324
Other revenue
Disaggregation of Revenue [Line Items]
Total revenues	54	2,601
Revenue recognized at a point in time
Disaggregation of Revenue [Line Items]
Total revenues	23,920	23,149
Revenue recognized at a point in time | Interchange and card revenue
Disaggregation of Revenue [Line Items]
Total revenues	6,643	8,244
Revenue recognized at a point in time | Servicing fees from Partner Bank
Disaggregation of Revenue [Line Items]
Total revenues	14,192	9,372
Revenue recognized at a point in time | Account fees
Disaggregation of Revenue [Line Items]
Total revenues	2,555	2,661
Revenue recognized at a point in time | University fees
Disaggregation of Revenue [Line Items]
Total revenues	476	271
Revenue recognized at a point in time | Other revenue
Disaggregation of Revenue [Line Items]
Total revenues	54	2,601
Revenue recognized over time
Disaggregation of Revenue [Line Items]
Total revenues	1,127	1,053
Revenue recognized over time | University fees
Disaggregation of Revenue [Line Items]
Total revenues	$ 1,127	$ 1,053