Net Sales (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021
Disaggregation of Revenue [Line Items]
Net sales	$ 1,178.1	$ 1,269.3	$ 3,990.3	$ 3,529.0
Engineered Materials
Disaggregation of Revenue [Line Items]
Net sales	242.7	230.8	839.2	477.5
Latex Binders
Disaggregation of Revenue [Line Items]
Net sales	340.9	315.6	1,001.3	877.6
Base Plastics
Disaggregation of Revenue [Line Items]
Net sales	293.4	393.3	1,051.8	1,119.3
Polystyrene
Disaggregation of Revenue [Line Items]
Net sales	247.7	274.8	877.7	855.0
Feedstocks
Disaggregation of Revenue [Line Items]
Net sales	53.4	54.8	220.3	199.6
United States
Disaggregation of Revenue [Line Items]
Net sales	312.5	275.0	985.4	629.5
United States | Engineered Materials
Disaggregation of Revenue [Line Items]
Net sales	128.9	102.4	418.0	174.1
United States | Latex Binders
Disaggregation of Revenue [Line Items]
Net sales	105.4	86.3	290.1	228.2
United States | Base Plastics
Disaggregation of Revenue [Line Items]
Net sales	73.7	82.3	264.3	216.5
United States | Feedstocks
Disaggregation of Revenue [Line Items]
Net sales	4.5	4.0	13.0	10.7
Europe
Disaggregation of Revenue [Line Items]
Net sales	612.6	703.8	2,194.5	2,022.0
Europe | Engineered Materials
Disaggregation of Revenue [Line Items]
Net sales	72.5	89.6	300.1	190.8
Europe | Latex Binders
Disaggregation of Revenue [Line Items]
Net sales	160.1	153.5	480.4	431.4
Europe | Base Plastics
Disaggregation of Revenue [Line Items]
Net sales	157.1	247.3	602.2	699.2
Europe | Polystyrene
Disaggregation of Revenue [Line Items]
Net sales	174.0	162.6	604.5	511.7
Europe | Feedstocks
Disaggregation of Revenue [Line Items]
Net sales	48.9	50.8	207.3	188.9
Asia-Pacific
Disaggregation of Revenue [Line Items]
Net sales	218.8	265.0	711.5	807.0
Asia-Pacific | Engineered Materials
Disaggregation of Revenue [Line Items]
Net sales	38.9	35.9	112.4	108.1
Asia-Pacific | Latex Binders
Disaggregation of Revenue [Line Items]
Net sales	72.9	73.0	223.9	211.1
Asia-Pacific | Base Plastics
Disaggregation of Revenue [Line Items]
Net sales	33.3	43.9	102.1	144.5
Asia-Pacific | Polystyrene
Disaggregation of Revenue [Line Items]
Net sales	73.7	112.2	273.1	343.3
Rest of World
Disaggregation of Revenue [Line Items]
Net sales	34.2	25.5	98.9	70.5
Rest of World | Engineered Materials
Disaggregation of Revenue [Line Items]
Net sales	2.4	2.9	8.7	4.5
Rest of World | Latex Binders
Disaggregation of Revenue [Line Items]
Net sales	2.5	2.8	6.9	6.9
Rest of World | Base Plastics
Disaggregation of Revenue [Line Items]
Net sales	$ 29.3	$ 19.8	83.2	$ 59.1
Rest of World | Polystyrene
Disaggregation of Revenue [Line Items]
Net sales			$ 0.1