Business and geographic segments - Total Assets Held by Business Segments (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Business and geographic segments
Total assets	$ 2,800.2	$ 2,737.0	$ 2,835.7
Depreciation and amortization	66.7	54.1	58.5
Capital expenditures	30.9	48.5	67.6
Corporate and eliminations
Business and geographic segments
Total assets	198.0	197.8	191.7
Chemicals | Operating Segment
Business and geographic segments
Total assets	2,268.5	2,196.8	2,293.5
Depreciation and amortization	62.9	49.9	53.1
Capital expenditures	29.5	47.4	63.2
Component products | Operating Segment
Business and geographic segments
Total assets	117.0	141.5	131.3
Depreciation and amortization	3.7	4.0	4.0
Capital expenditures	1.4	1.1	3.7
Real estate management and development | Operating Segment
Business and geographic segments
Total assets	216.7	200.9	219.2
Depreciation and amortization	$ 0.1	$ 0.2	1.4
Capital expenditures			$ 0.7