BUSINESS SEGMENT INFORMATION - Segment Information (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Mar. 31, 2026	Mar. 31, 2025	Mar. 31, 2026	Mar. 31, 2025
Depreciation, depletion and amortization expense:
Total depreciation, depletion and amortization expense			$ 117.5	$ 133.9
Continuing Operations
Depreciation, depletion and amortization expense:
Total depreciation, depletion and amortization expense	$ 57.2	$ 57.1	117.5	115.6
Capital Expenditure [Abstract]
Total capital expenditures	37.2	40.3	72.4	71.0
Continuing Operations | Operating Segments
Capital Expenditure [Abstract]
Total capital expenditures	33.4	38.7	65.4	67.3
Continuing Operations | Corporate and other
Capital Expenditure [Abstract]
Total capital expenditures	3.8	1.6	7.0	3.7
Customized Polymer Solutions | Continuing Operations
Depreciation, depletion and amortization expense:
Total depreciation, depletion and amortization expense	25.0	22.9	52.9	45.9
Customized Polymer Solutions | Continuing Operations | Operating Segments
Capital Expenditure [Abstract]
Total capital expenditures	16.7	7.0	27.9	16.9
Durable Metal Solutions | Continuing Operations
Depreciation, depletion and amortization expense:
Total depreciation, depletion and amortization expense	7.6	7.0	15.2	14.2
Durable Metal Solutions | Continuing Operations | Operating Segments
Capital Expenditure [Abstract]
Total capital expenditures	6.3	7.4	13.2	14.2
Sustainable Fiber Solutions | Continuing Operations
Depreciation, depletion and amortization expense:
Total depreciation, depletion and amortization expense	23.3	25.7	46.7	52.3
Sustainable Fiber Solutions | Continuing Operations | Operating Segments
Capital Expenditure [Abstract]
Total capital expenditures	8.9	23.4	19.3	34.8
Innovative Closure Solutions | Continuing Operations
Depreciation, depletion and amortization expense:
Total depreciation, depletion and amortization expense	1.3	1.5	2.7	3.2
Innovative Closure Solutions | Continuing Operations | Operating Segments
Capital Expenditure [Abstract]
Total capital expenditures	$ 1.5	$ 0.9	$ 5.0	$ 1.4