GOODWILL AND INTANGIBLE ASSETS - Changes in Goodwill (Details) $ in Thousands	9 Months Ended
	Jun. 30, 2022 USD ($)
Goodwill [Roll Forward]
Goodwill, beginning	$ 292,243
Goodwill attributable to preliminary purchase price adjustments and acquisitions during the nine months ended June 30, 2022	61,639
Goodwill, ending	353,882
Merchant Services
Goodwill [Roll Forward]
Goodwill, beginning	119,086
Goodwill attributable to preliminary purchase price adjustments and acquisitions during the nine months ended June 30, 2022	0
Goodwill, ending	119,086
Proprietary Software and Payments
Goodwill [Roll Forward]
Goodwill, beginning	173,157
Goodwill attributable to preliminary purchase price adjustments and acquisitions during the nine months ended June 30, 2022	61,639
Goodwill, ending	234,796
Other
Goodwill [Roll Forward]
Goodwill, beginning	0
Goodwill attributable to preliminary purchase price adjustments and acquisitions during the nine months ended June 30, 2022	0
Goodwill, ending	$ 0