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RESTRUCTURING ACTIVITIES - 2025 Restructuring Plan (Details) - USD ($) $ in Millions	3 Months Ended	6 Months Ended	9 Months Ended
	Jun. 30, 2026	Jun. 30, 2026	Jun. 30, 2026
RESTRUCTURING ACTIVITIES
Accretion expense		$ 1.9
2025 Restructuring plan
RESTRUCTURING ACTIVITIES
Net pre-tax restructuring charges	$ 8.1	16.1	$ 146.1
Change in cost estimate of asset retirement obligation		1.4
Activities
Reserve balance at December 31, 2025		33.0
Restructuring charges (credits)		12.8
Payments		(16.5)
Asset write-offs		(1.7)
Reserve balance at June 30, 2026	27.6	27.6	27.6
2025 Restructuring plan \| Severance and related benefit credits (credits)
RESTRUCTURING ACTIVITIES
Net pre-tax restructuring charges	(3.0)	(3.0)	7.9
Activities
Reserve balance at December 31, 2025		11.1
Restructuring charges (credits)		(3.0)
Payments		(0.5)
Reserve balance at June 30, 2026	7.6	7.6	7.6
2025 Restructuring plan \| Asset Related Charges
RESTRUCTURING ACTIVITIES
Net pre-tax restructuring charges	4.5	9.6	107.2
Activities
Restructuring charges (credits)		6.3
Payments		(4.6)
Asset write-offs		(1.7)
2025 Restructuring plan \| Accelerated depreciation for the asset retirement cost
RESTRUCTURING ACTIVITIES
Net pre-tax restructuring charges		1.9	34.5
2025 Restructuring plan \| Accelerated depreciation charges of plant, property and equipment associated with the exit
RESTRUCTURING ACTIVITIES
Net pre-tax restructuring charges			55.9
2025 Restructuring plan \| Decommissioning and other charges
RESTRUCTURING ACTIVITIES
Net pre-tax restructuring charges			16.8
2025 Restructuring plan \| Contract terminations
RESTRUCTURING ACTIVITIES
Net pre-tax restructuring charges	6.6	9.5	31.0
Activities
Reserve balance at December 31, 2025		21.9
Restructuring charges (credits)		9.5
Payments		(11.4)
Reserve balance at June 30, 2026	20.0	20.0	20.0
2025 Restructuring plan \| Employee termination benefits
Activities
Reserve balance at December 31, 2025		11.1
Reserve balance at June 30, 2026	7.6	7.6	7.6
2025 Restructuring plan \| Engineered Materials
RESTRUCTURING ACTIVITIES
Net pre-tax restructuring charges	5.9	12.5
Accretion expense			2.5
2025 Restructuring plan \| Engineered Materials \| Asset Related Charges
RESTRUCTURING ACTIVITIES
Restructuring costs expected to incur	4.4	4.4	4.4
2025 Restructuring plan \| Engineered Materials \| Decommissioning and other charges
RESTRUCTURING ACTIVITIES
Restructuring costs expected to incur	1.9	1.9	1.9
2025 Restructuring plan \| Engineered Materials \| Contract terminations \| Minimum
RESTRUCTURING ACTIVITIES
Restructuring costs expected to incur	2.0	2.0	2.0
2025 Restructuring plan \| Engineered Materials \| Contract terminations \| Maximum
RESTRUCTURING ACTIVITIES
Restructuring costs expected to incur	5.0	5.0	5.0
2025 Restructuring plan \| Polymer Solutions
RESTRUCTURING ACTIVITIES
Net pre-tax restructuring charges	2.2	3.6
2025 Restructuring plan \| Polymer Solutions \| Asset related charges, accretion expense
RESTRUCTURING ACTIVITIES
Restructuring costs expected to incur	$ 0.5	$ 0.5	$ 0.5