BUSINESS SEGMENT INFORMATION - Geographic Area (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Mar. 31, 2026	Mar. 31, 2025	Mar. 31, 2026	Mar. 31, 2025
Segment Reporting Information [Line Items]
Net sales by geographic area:	$ 1,072.8	$ 1,078.4	$ 2,067.6	$ 2,095.1
Raw material costs	553.0	609.7	1,068.3	1,192.3
Manufacturing costs	272.8	220.2	549.7	454.9
Costs of products sold	825.8	829.9	1,618.0	1,647.2
Selling, general and administrative expenses	191.7	159.9	337.8	320.1
Acquisition and integration related costs	1.4	1.3	2.1	4.1
Restructuring charges and other	15.7	9.1	29.9	12.4
Non-cash asset impairment charges	4.5	17.2	4.7	17.5
Loss (gain) on disposal of properties, plants and equipment, net	(1.7)	0.1	(217.4)	(2.3)
Loss on disposal of businesses, net	0.0	0.2	0.5	1.3
Operating profit	35.4	60.7	292.0	94.8
Customized Polymer Solutions
Segment Reporting Information [Line Items]
Net sales by geographic area:	344.8	322.5	649.9	616.9
Raw material costs	153.0	155.0	288.8	305.6
Manufacturing costs	117.7	90.7	229.2	175.9
Costs of products sold	270.7	245.7	518.0	481.5
Selling, general and administrative expenses	66.6	56.3	118.4	109.5
Acquisition and integration related costs	0.7	1.3	1.4	4.1
Restructuring charges and other	3.9	0.6	6.2	1.7
Non-cash asset impairment charges	0.0	0.7	0.0	1.0
Loss (gain) on disposal of properties, plants and equipment, net	0.4	0.1	0.4	0.2
Loss on disposal of businesses, net		0.0	0.5	0.0
Operating profit	2.5	17.8	5.0	18.9
Durable Metal Solutions
Segment Reporting Information [Line Items]
Net sales by geographic area:	380.4	372.9	735.2	728.8
Raw material costs	211.2	236.3	411.2	472.9
Manufacturing costs	79.9	52.8	164.0	103.1
Costs of products sold	291.1	289.1	575.2	576.0
Selling, general and administrative expenses	48.1	40.8	82.2	80.3
Acquisition and integration related costs	0.0	0.0	0.0	0.0
Restructuring charges and other	4.6	0.7	8.4	1.4
Non-cash asset impairment charges	0.0	2.1	0.0	2.1
Loss (gain) on disposal of properties, plants and equipment, net	(2.4)	(1.1)	(2.5)	(3.9)
Loss on disposal of businesses, net		0.2	0.0	1.3
Operating profit	39.0	41.1	71.9	71.6
Sustainable Fiber Solutions
Segment Reporting Information [Line Items]
Net sales by geographic area:	321.8	360.7	633.7	704.7
Raw material costs	179.0	208.6	357.3	394.0
Manufacturing costs	71.5	74.0	139.9	168.3
Costs of products sold	250.5	282.6	497.2	562.3
Selling, general and administrative expenses	69.6	57.6	123.7	119.1
Acquisition and integration related costs	0.0	0.0	0.0	0.0
Restructuring charges and other	7.1	7.6	15.1	9.0
Non-cash asset impairment charges	4.5	14.0	4.7	14.0
Loss (gain) on disposal of properties, plants and equipment, net	0.3	1.1	(215.3)	1.4
Loss on disposal of businesses, net		0.0	0.0	0.0
Operating profit	(10.2)	(2.2)	208.3	(1.1)
Innovative Closure Solutions
Segment Reporting Information [Line Items]
Net sales by geographic area:	25.8	22.3	48.8	44.7
Raw material costs	9.8	9.8	11.0	19.8
Manufacturing costs	3.7	2.7	16.6	7.6
Costs of products sold	13.5	12.5	27.6	27.4
Selling, general and administrative expenses	7.4	5.2	13.5	11.2
Acquisition and integration related costs	0.7	0.0	0.7	0.0
Restructuring charges and other	0.1	0.2	0.2	0.3
Non-cash asset impairment charges	0.0	0.4	0.0	0.4
Loss (gain) on disposal of properties, plants and equipment, net	0.0	0.0	0.0	0.0
Loss on disposal of businesses, net		0.0	0.0	0.0
Operating profit	4.1	4.0	6.8	5.4
United States
Segment Reporting Information [Line Items]
Net sales by geographic area:	531.0	571.3	1,024.8	1,095.1
United States | Customized Polymer Solutions
Segment Reporting Information [Line Items]
Net sales by geographic area:	145.7	142.6	270.4	264.7
United States | Durable Metal Solutions
Segment Reporting Information [Line Items]
Net sales by geographic area:	67.8	72.8	130.3	136.8
United States | Sustainable Fiber Solutions
Segment Reporting Information [Line Items]
Net sales by geographic area:	311.0	349.5	611.4	681.0
United States | Innovative Closure Solutions
Segment Reporting Information [Line Items]
Net sales by geographic area:	6.5	6.4	12.7	12.6
Europe, Middle East and Africa
Segment Reporting Information [Line Items]
Net sales by geographic area:	383.0	356.8	730.0	686.0
Europe, Middle East and Africa | Customized Polymer Solutions
Segment Reporting Information [Line Items]
Net sales by geographic area:	147.5	131.2	275.2	247.2
Europe, Middle East and Africa | Durable Metal Solutions
Segment Reporting Information [Line Items]
Net sales by geographic area:	223.4	215.4	432.8	418.0
Europe, Middle East and Africa | Sustainable Fiber Solutions
Segment Reporting Information [Line Items]
Net sales by geographic area:	0.2	0.2	0.5	0.4
Europe, Middle East and Africa | Innovative Closure Solutions
Segment Reporting Information [Line Items]
Net sales by geographic area:	11.9	10.0	21.5	20.4
Asia Pacific and Other Americas
Segment Reporting Information [Line Items]
Net sales by geographic area:	158.8	150.3	312.8	314.0
Asia Pacific and Other Americas | Customized Polymer Solutions
Segment Reporting Information [Line Items]
Net sales by geographic area:	51.6	48.7	104.3	105.0
Asia Pacific and Other Americas | Durable Metal Solutions
Segment Reporting Information [Line Items]
Net sales by geographic area:	89.2	84.7	172.1	174.0
Asia Pacific and Other Americas | Sustainable Fiber Solutions
Segment Reporting Information [Line Items]
Net sales by geographic area:	10.6	11.0	21.8	23.3
Asia Pacific and Other Americas | Innovative Closure Solutions
Segment Reporting Information [Line Items]
Net sales by geographic area:	$ 7.4	$ 5.9	$ 14.6	$ 11.7