Segmental Information - Financial information by reportable segment (Details) - USD ($) $ in Millions	3 Months Ended
Mar. 31, 2019	Apr. 01, 2018	Dec. 31, 2018
Segment Reporting Information [Line Items]
Net sales	$ 120.4	$ 119.7
Adjusted EBITDA	18.5	19.2
Depreciation and amortization	3.7	4.9
Restructuring charges	9.0	0.7
Total assets	423.8		$ 408.8
Capital expenditures	3.7	1.4
Gas Cylinders segment
Segment Reporting Information [Line Items]
Net sales	58.4	59.3
Adjusted EBITDA	4.5	6.0
Depreciation and amortization	1.4	1.9
Restructuring charges	8.9	0.2
Elektron segment
Segment Reporting Information [Line Items]
Net sales	62.0	60.4
Adjusted EBITDA	14.0	13.2
Depreciation and amortization	2.3	3.0
Restructuring charges	0.1	0.5
Operating Segments \| Gas Cylinders segment
Segment Reporting Information [Line Items]
Total assets	162.3		156.3
Capital expenditures	1.1	0.4
Operating Segments \| Elektron segment
Segment Reporting Information [Line Items]
Total assets	227.1		218.2
Capital expenditures	2.6	1.0
Corporate, Non-Segment
Segment Reporting Information [Line Items]
Total assets	34.4		$ 34.3
Capital expenditures	$ 0.0	$ 0.0

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Capital Expenditure, Cash And Noncash

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Sum of the carrying amounts as of the balance sheet date of all assets that are recognized. Assets are probable future economic benefits obtained or controlled by an entity as a result of past transactions or events.

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Amount, excluding tax collected from customer, of revenue from satisfaction of performance obligation by transferring promised good or service to customer. Tax collected from customer is tax assessed by governmental authority that is both imposed on and concurrent with specific revenue-producing transaction, including, but not limited to, sales, use, value added and excise.

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