Segmental Information - Financial information by reportable segment (Details) - USD ($) $ in Millions	3 Months Ended	6 Months Ended
Jun. 30, 2019	Jul. 01, 2018	Jun. 30, 2019	Jul. 01, 2018	Dec. 31, 2018
Segment Reporting Information [Line Items]
Net sales	$ 116.5	$ 128.2	$ 236.9	$ 247.9
Adjusted EBITDA	20.2	21.4	38.7	40.6
Depreciation and amortization	4.0	4.9	7.7	9.8
Restructuring charges	12.7	0.3	21.7	1.0
Total assets	412.1		412.1		$ 408.8
Capital expenditures	3.9	2.4	7.6	3.8
Gas Cylinders
Segment Reporting Information [Line Items]
Net sales	58.1	60.4	116.5	119.7
Adjusted EBITDA	7.1	5.0	11.6	11.0
Depreciation and amortization	1.4	1.9	2.8	3.9
Restructuring charges	8.3	(0.1)	17.2	0.1
Elektron
Segment Reporting Information [Line Items]
Net sales	58.4	67.8	120.4	128.2
Adjusted EBITDA	13.1	16.4	27.1	29.6
Depreciation and amortization	2.6	3.0	4.9	5.9
Restructuring charges	4.4	0.4	4.5	0.9
Operating Segments \| Gas Cylinders
Segment Reporting Information [Line Items]
Total assets	161.5		161.5		156.3
Capital expenditures	1.3	0.3	2.4	0.7
Operating Segments \| Elektron
Segment Reporting Information [Line Items]
Total assets	214.2		214.2		218.2
Capital expenditures	2.6	2.1	5.2	3.1
Corporate, Non-Segment
Segment Reporting Information [Line Items]
Total assets	36.4		36.4		$ 34.3
Capital expenditures	$ 0.0	$ 0.0	$ 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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The aggregate expense recognized in the current period that allocates the cost of tangible assets, intangible assets, or depleting assets to periods that benefit from use of the assets.

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Amount of expenses associated with exit or disposal activities pursuant to an authorized plan. Excludes expenses related to a discontinued operation or an asset retirement obligation.

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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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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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