FINANCIAL INSTRUMENTS AND FAIR VALUE MEASUREMENTS - Additional Information (Details) - USD ($) $ in Millions	3 Months Ended
	Dec. 31, 2025	Dec. 31, 2024	Sep. 30, 2025
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Gains recorded in interest expense	$ (9.7)	$ (15.9)
Carrying value of impaired asset	0.7	0.3
Long-lived assets, fair value	0.5	0.0
Impairment of long lived assets	0.2	0.3
Customized Polymer Solutions
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Impairment of long lived assets	0.2	0.3
Interest rate derivatives | Cash Flow Hedging
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Derivative, notional amount	$ 275.0		$ 562.5
Derivative, forward interest rate	1.16%
Gains reclassified to earnings	$ 2.0	6.2
Gain to be reclassified within next twelve months	7.5
Foreign Currency Forward Contracts
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Derivative, notional amount	118.2		165.0
Gain (loss) recorded under fair value contracts	0.3	(1.9)
Unrealized (losses) gains on foreign currency	(0.8)	0.1
Cross currency swap
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Derivative, notional amount	$ 534.9		$ 534.9
Derivative, forward interest rate	1.64%
Gains recorded in interest expense	$ 2.2	$ 1.5