Revenue - disaggregation of sales - Schedule of Disaggregates of Net Sales of our Chemicals Segment (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2025	Mar. 31, 2024
Revenue - disaggregation of sales [Line Items]
Net sales	$ 538.6	$ 530.6
Chemicals
Revenue - disaggregation of sales [Line Items]
Net sales	489.8	478.8
Point of Origin | Chemicals
Revenue - disaggregation of sales [Line Items]
Net sales	489.8	478.8
Point of Origin | Chemicals | Eliminations
Revenue - disaggregation of sales [Line Items]
Net sales	(296.4)	(204.2)
Point of Origin | Chemicals | Operating Segment | United States
Revenue - disaggregation of sales [Line Items]
Net sales	322.4	240.9
Point of Origin | Chemicals | Operating Segment | Germany
Revenue - disaggregation of sales [Line Items]
Net sales	216.8	212.2
Point of Origin | Chemicals | Operating Segment | Canada
Revenue - disaggregation of sales [Line Items]
Net sales	110.8	89.3
Point of Origin | Chemicals | Operating Segment | Norway
Revenue - disaggregation of sales [Line Items]
Net sales	70.5	71.0
Point of Origin | Chemicals | Operating Segment | Belgium
Revenue - disaggregation of sales [Line Items]
Net sales	65.7	69.6
Point of Destination | Chemicals
Revenue - disaggregation of sales [Line Items]
Net sales	489.8	478.8
Point of Destination | Chemicals | Operating Segment | Europe
Revenue - disaggregation of sales [Line Items]
Net sales	228.5	214.9
Point of Destination | Chemicals | Operating Segment | North America
Revenue - disaggregation of sales [Line Items]
Net sales	190.2	166.0
Point of Destination | Chemicals | Operating Segment | Other
Revenue - disaggregation of sales [Line Items]
Net sales	$ 71.1	$ 97.9