DISCONTINUED OPERATIONS - Cash Flow (Details) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2023
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Depreciation and amortization	$ 27,900	$ 25,553	$ 23,320
Equity-based compensation	18,344	26,338	27,878
Gain on sale of businesses	(25,960)	(205,576)	0
Write down of intangible asset	0	0	2,660
Provision for deferred income taxes	4,974	434	(5,935)
Non-cash lease expense	2,515	4,471	4,683
Increase (decrease) in non-cash contingent consideration expense from original estimate	1,536	(690)	10,781
Contingent consideration paid in excess of original estimates	(760)	(6,567)	(19,303)
Expenditures for property and equipment	(1,941)	(2,964)	(4,204)
Expenditures for capitalized software	(8,194)	(11,996)	(12,171)
Purchases of merchant portfolios and residual buyouts	(12)	(5,372)	(2,191)
Acquisitions of businesses, net of cash and restricted cash acquired	(11,000)	(19,100)	(101,998)
Cash paid for contingent consideration up to original estimates	(817)	(760)	(6,832)
Healthcare RCM Business
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Proceeds from sale of Merchant Services Business, net of cash sold	96,102	0	0
Merchant Services Business
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Proceeds from sale of Merchant Services Business, net of cash sold	0	435,058	0
Discontinued Operations, Held-for-Sale or Disposed of by Sale | Healthcare RCM Business
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Depreciation and amortization	1,940	3,243	3,118
Equity-based compensation	3,112	2,783	2,859
Gain on sale of businesses	(25,960)	0	0
Non-cash lease expense	702	1,235	1,221
Increase (decrease) in non-cash contingent consideration expense from original estimate	1,302	(712)	788
Contingent consideration paid in excess of original estimates	(700)	0	0
Expenditures for property and equipment	(156)	(294)	(119)
Expenditures for capitalized software	(263)	(423)	(397)
Proceeds from sale of Merchant Services Business, net of cash sold	96,102	0	0
Cash paid for contingent consideration up to original estimates	$ (800)	0	(385)
Discontinued Operations, Held-for-Sale or Disposed of by Sale | Merchant Services Business
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Depreciation and amortization		8,649	10,023
Equity-based compensation		8,160	4,155
Provision for doubtful accounts		26	(19)
Gain on sale of businesses		(205,576)	0
Amortization of capitalized customer acquisition costs		873	746
Write down of intangible asset		0	2,660
Provision for deferred income taxes		32	378
Non-cash lease expense		802	1,032
Contingent consideration paid in excess of original estimates		0	(3,211)
Expenditures for property and equipment		(705)	(1,540)
Expenditures for capitalized software		(957)	(1,612)
Purchases of merchant portfolios and residual buyouts		(5,372)	(2,191)
Acquisitions of businesses, net of cash and restricted cash acquired		0	(4,497)
Acquisition of other intangibles		(11)	(420)
Proceeds from sale of Merchant Services Business, net of cash sold		$ 435,058	$ 0