Business and geographic segments - Depreciation and Amortization (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2025	Dec. 31, 2024	Dec. 31, 2023
Business and geographic segments
Depreciation and amortization	$ 66.4	$ 66.7	$ 54.1
Operating Segment
Business and geographic segments
Depreciation and amortization	66.4	66.7	54.1
Chemicals \| Operating Segment
Business and geographic segments
Depreciation and amortization	62.7	62.9	49.9
Component products \| Operating Segment
Business and geographic segments
Depreciation and amortization	$ 3.7	3.7	4.0
Real estate management and development \| Operating Segment
Business and geographic segments
Depreciation and amortization		$ 0.1	$ 0.2

The current period expense charged against earnings on long-lived, physical assets not used in production, and which are not intended for resale, to allocate or recognize the cost of such assets over their useful lives; or to record the reduction in book value of an intangible asset over the benefit period of such asset; or to reflect consumption during the period of an asset that is not used in production.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Name Accounting Standards Codification
-Section 45
-Paragraph 28
-Subparagraph (b)
-SubTopic 10
-Topic 230
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482740/230-10-45-28

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Name Accounting Standards Codification
-Topic 360
-SubTopic 10
-Section 50
-Paragraph 1
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482099/360-10-50-1

Name:	us-gaap_DepreciationAndAmortization
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration