DEBT - Schedule of Debt Repurchase Activity (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2022
Debt Instrument [Line Items]
Gain on Early Extinguishment	$ 2.6	$ (3.0)	$ 0.0
Senior Notes
Debt Instrument [Line Items]
Amounts Repurchased	180.1	61.4
Amounts Paid	172.9	52.7
Unamortized Debt Issuance Costs	2.5	0.8
Gain on Early Extinguishment	4.7	7.9
2029 Notes
Debt Instrument [Line Items]
Amounts Repurchased	284.2
Amounts Paid	284.2
Unamortized Debt Issuance Costs	2.9
Gain on Early Extinguishment	(2.9)
2029 Notes | Senior Notes
Debt Instrument [Line Items]
Amounts Repurchased	8.1	2.8
Amounts Paid	7.8	2.6
Unamortized Debt Issuance Costs	0.1	0.0
Gain on Early Extinguishment	0.2	0.2
2030 Notes
Debt Instrument [Line Items]
Amounts Repurchased	142.5
Amounts Paid	142.5
Unamortized Debt Issuance Costs	2.0
Gain on Early Extinguishment	(2.0)
2030 Notes | Senior Notes
Debt Instrument [Line Items]
Amounts Repurchased	132.8	11.5
Amounts Paid	130.5	10.7
Unamortized Debt Issuance Costs	2.0	0.2
Gain on Early Extinguishment	0.3	0.6
2031 Notes
Debt Instrument [Line Items]
Amounts Repurchased	285.7
Amounts Paid	277.7
Unamortized Debt Issuance Costs	3.0
Gain on Early Extinguishment	5.0
2031 Notes | Senior Notes
Debt Instrument [Line Items]
Amounts Repurchased	39.2	47.1
Amounts Paid	34.6	39.4
Unamortized Debt Issuance Costs	0.4	0.6
Gain on Early Extinguishment	$ 4.2	$ 7.1