FINANCIAL INSTRUMENTS AND FAIR VALUE MEASUREMENTS - Additional Information (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Mar. 31, 2026	Mar. 31, 2025	Mar. 31, 2026	Mar. 31, 2025	Sep. 30, 2025
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Gains recorded in interest expense	$ (10.0)	$ (15.5)	$ (19.7)	$ (31.4)
Carrying value of impaired asset	7.6	38.1	7.6	38.1
Long-lived assets, fair value	2.9	20.6	2.9	20.6
Impairment of long lived assets			4.7	17.5
Customized Polymer Solutions
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Impairment of long lived assets			4.7	1.0
Durable Metal Solutions
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Impairment of long lived assets				2.1
Sustainable Fiber Solutions
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Impairment of long lived assets				14.0
Innovative Closure Solutions
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Impairment of long lived assets				0.2
Impairment of intangible assets, finite-lived				0.2
Interest rate derivatives | Cash Flow Hedging
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Derivative, notional amount	$ 320.0		$ 320.0		$ 562.5
Derivative, forward interest rate	1.71%		1.71%
Gains reclassified to earnings	$ 1.8	4.8	$ 3.8	11.0
Gain to be reclassified within next twelve months			7.7
Foreign Currency Forward Contracts
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Derivative, notional amount	112.8		112.8		165.0
Gain (loss) recorded under fair value contracts	(0.2)	0.8	0.1	(1.1)
Unrealized gains (losses) on foreign currency	0.7	(0.3)	(0.1)	(0.2)
Cross currency swap
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Derivative, notional amount	$ 534.9		$ 534.9		$ 534.9
Derivative, forward interest rate	1.64%		1.64%
Gains recorded in interest expense	$ 2.2	$ 1.7	$ 4.4	$ 3.2