EQUITY - Accumulated Other Comprehensive Loss (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2021
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Other comprehensive income (loss) before reclassifications	$ (24.8)	$ (96.4)	$ 35.1
Amounts reclassified from accumulated other comprehensive net income (loss)	76.4	2.6	7.7
Income tax benefit (expense)	(19.8)	15.6	(10.0)
Net current period other comprehensive income (loss)	31.8	(78.2)	32.8
Accumulated Other Comprehensive Income (Loss)
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Equity beginning balance	(144.6)	(66.4)	(99.1)
Equity ending balance	(112.8)	(144.6)	(66.4)
Foreign Currency Translation Adjustments
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Equity beginning balance	(28.9)	(1.7)	(6.2)
Other comprehensive income (loss) before reclassifications	7.0	(27.2)	4.5
Amounts reclassified from accumulated other comprehensive net income (loss)	0.0	0.0	0.0
Income tax benefit (expense)	0.0	0.0	0.0
Net current period other comprehensive income (loss)	7.0	(27.2)	4.5
Equity ending balance	(21.9)	(28.9)	(1.7)
Net Unrealized Gain (Loss) On Derivative Instruments
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Equity beginning balance	33.3	10.2	(15.1)
Other comprehensive income (loss) before reclassifications	5.6	40.1	26.8
Amounts reclassified from accumulated other comprehensive net income (loss)	(23.3)	(9.1)	7.3
Income tax benefit (expense)	4.5	(7.9)	(8.9)
Net current period other comprehensive income (loss)	(13.2)	23.1	25.2
Equity ending balance	20.1	33.3	10.2
Net Unrealized Loss On Securities
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Equity beginning balance	(79.7)	(2.3)	0.0
Other comprehensive income (loss) before reclassifications	(34.9)	(102.0)	(3.1)
Amounts reclassified from accumulated other comprehensive net income (loss)	101.3	0.0	0.0
Income tax benefit (expense)	(25.3)	24.6	0.8
Net current period other comprehensive income (loss)	41.1	(77.4)	(2.3)
Equity ending balance	(38.6)	(79.7)	(2.3)
Pension and Other Post- Retirement Benefit Adjustments
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Equity beginning balance	(69.3)	(72.5)	(77.8)
Other comprehensive income (loss) before reclassifications	(2.5)	(7.3)	6.9
Amounts reclassified from accumulated other comprehensive net income (loss)	(1.6)	11.7	0.4
Income tax benefit (expense)	1.0	(1.1)	(1.9)
Net current period other comprehensive income (loss)	(3.1)	3.3	5.4
Equity ending balance	$ (72.4)	$ (69.3)	$ (72.5)