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EQUITY-BASED COMPENSATION - Additional Information (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		6 Months Ended
	Mar. 31, 2025	Mar. 31, 2024	Mar. 31, 2025	Mar. 31, 2024	May 31, 2021	Sep. 30, 2020	May 31, 2018
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Equity-based compensation expense	$ 3,932	$ 5,022	$ 7,746	$ 10,380
Income tax expense (benefits) related to equity-based compensation	(1,378)	816	(767)	1,713
Stock options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Equity-based compensation expense	1,572	4,078	$ 3,988	8,314
Granted, weighted average grant date fair value (in USD per share)			$ 13.07
Unrecognized compensation expense related to unvested options at end of period	12,072		$ 12,072
Period for recognition of unrecognized compensation cost			2 years 6 months
Fair value of stock options that vested	6,822		$ 10,031
Restricted stock units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Equity-based compensation expense	2,360	944	$ 3,758	2,066
Period for recognition of unrecognized compensation cost			3 years
Cost not yet recognized, amount	21,428		$ 21,428
Vested in period, fair value	$ 3,658		$ 4,066
2018 Equity Incentive Award Plan \| Stock options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares available for grant under the plan (in shares)	2,233,833		2,233,833				3,500,000
Additional Class A common shares added at the beginning of calendar year as percentage of common stock outstanding at end of previous year (percent)							4.00%
2020 Equity Incentive Award Plan \| Stock options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares available for grant under the plan (in shares)	1,567,739		1,567,739		3,000,000	1,500,000
Discontinued Operations, Held-for-Sale or Disposed of by Sale \| Merchant Services Business
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Equity-based compensation expense		$ 755		$ 1,905