EQUITY - Accumulated Other Comprehensive Loss (Details) - USD ($) $ in Millions		12 Months Ended
		Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2019
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Equity beginning balance		$ 697.2
Other comprehensive income (loss) before reclassifications		35.1	$ (22.1)	$ (46.3)
Amounts reclassified from accumulated other comprehensive net income (loss)		7.7	11.2	3.3
Income tax benefit (expense)		(10.0)	5.7	8.9
Net current period other comprehensive income (loss)		32.8	(5.2)	(34.1)
Equity ending balance		1,013.3	697.2
Accumulated Other Comprehensive Income (Loss)
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Equity beginning balance		(99.1)	(93.9)	(46.0)
Equity ending balance		(66.4)	(99.1)	(93.9)
Accumulated Other Comprehensive Income (Loss) | Cumulative Effect, Period of Adoption, Adjustment
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Equity beginning balance	[1],[2]			(13.8)
Foreign Currency Translation Adjustments
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Equity beginning balance		(6.2)	(17.4)	(8.7)
Other comprehensive income (loss) before reclassifications		4.5	10.5	(11.2)
Amounts reclassified from accumulated other comprehensive net income (loss)		0.0	0.8	2.5
Income tax benefit (expense)		0.0	0.0	0.0
Net current period other comprehensive income (loss)		4.5	11.3	(8.7)
Equity ending balance		1.7	(6.2)	(17.4)
Net Unrealized Gain (Loss) On Derivative Instruments
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Equity beginning balance		(15.1)	(8.1)	8.3
Other comprehensive income (loss) before reclassifications		26.8	(19.7)	(20.1)
Amounts reclassified from accumulated other comprehensive net income (loss)		7.3	10.1	(2.0)
Income tax benefit (expense)		(8.9)	2.5	5.7
Net current period other comprehensive income (loss)		25.2	(7.1)	(16.4)
Equity ending balance		10.2	(15.1)	(8.1)
Net Unrealized Loss On Securities
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Equity beginning balance		0.0	0.0	0.0
Other comprehensive income (loss) before reclassifications		(3.1)	0.0	0.0
Amounts reclassified from accumulated other comprehensive net income (loss)		0.0	0.0	0.0
Income tax benefit (expense)		0.8	0.0	0.0
Net current period other comprehensive income (loss)		(2.3)	0.0	0.0
Equity ending balance		(2.3)	0.0	0.0
Net Unrealized Gain (Loss) in Pension and Other Post-Retirement Benefits
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Equity beginning balance		(77.8)	(68.4)	(45.6)
Other comprehensive income (loss) before reclassifications		6.9	(12.9)	(15.0)
Amounts reclassified from accumulated other comprehensive net income (loss)		0.4	0.3	2.8
Income tax benefit (expense)		(1.9)	3.2	3.2
Net current period other comprehensive income (loss)		5.4	(9.4)	(9.0)
Equity ending balance		$ 72.5	$ (77.8)	(68.4)
Net Unrealized Gain (Loss) in Pension and Other Post-Retirement Benefits | Cumulative Effect, Period of Adoption, Adjustment
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Equity beginning balance				$ (13.8)

[1] As a result of adopting ASU No. 2014-09, “Revenue from Contracts with Customers (ASC 606),” on October 1, 2018, the Company recorded a $9.1 cumulative effect of initially applying the new guidance as an adjustment to the fiscal year 2019 opening balance of retained earnings.

[2] As a result of adopting ASU No. 2018-02, “Reclassification of Certain Tax Effects from Accumulated Other Comprehensive Income,” on October 1, 2018, the Company reclassified $13.8 from accumulated other comprehensive loss to retained earnings in the fiscal year 2019 opening balances.