DESCRIPTION OF THE BUSINESS AND MERGER TRANSACTION - Narrative (Details) $ / shares in Units, $ in Thousands		3 Months Ended						9 Months Ended		12 Months Ended
	Jan. 04, 2021 USD ($) shares	Sep. 30, 2021 USD ($) $ / shares	Jun. 30, 2021 USD ($) $ / shares	Mar. 31, 2021 USD ($) $ / shares	Sep. 30, 2020 USD ($) $ / shares	Jun. 30, 2020 USD ($)	Mar. 31, 2020 USD ($)	Sep. 30, 2021 USD ($) revenue_source $ / shares	Sep. 30, 2020 USD ($) $ / shares	Dec. 31, 2020 USD ($)
Business Description And Reverse Recapitalization [Abstract]
Number of primary revenue sources | revenue_source								4
Proceeds used to pay down outstanding debt	$ 15,600
Cash received	$ 1,300
Recapitalization transaction (in shares) | shares	6,076,946
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Decrease to accounts receivable		$ (4,498)						$ (4,498)		$ (7,384)
Decrease to revenues		(21,974)			$ (18,338)			(69,250)	$ (49,528)
Decrease to net income		$ (8,794)	$ 1,836	$ (18,889)	$ (250)	$ 4,119	$ 4,534	$ (25,847)	$ 8,403
Decrease to basic EPS (in dollars per share) | $ / shares		$ (0.74)			$ (0.04)			$ (2.24)	$ 1.37
Decrease to diluted EPS (in dollars per share) | $ / shares		$ (0.74)			$ (0.04)			$ (0.65)	$ 1.37
Interchange and card revenue
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Decrease to revenues		$ (5,572)			$ (7,377)			$ (21,109)	$ (20,053)
Out of period adjustment
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Decrease to accounts receivable		800						$ 800
Decrease to revenues			200	200						400
Decrease to net income			$ 200	$ 200						$ 400
Decrease to basic EPS (in dollars per share) | $ / shares			$ 0.02	$ 0.02
Decrease to diluted EPS (in dollars per share) | $ / shares			$ 0.02	$ 0.01
Out of period adjustment | Interchange and card revenue
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Decrease to revenues		$ 800