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Income Taxes - Additional Information (Detail) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Mar. 31, 2018	Dec. 31, 2017	Jun. 30, 2018	Dec. 31, 2016
Income Tax Contingency [Line Items]
Accrued net interest and penalties	$ 0.2	$ 0.2
Unrecognized tax benefits, income tax interest and penalties accrued		0.3	$ 0.5
Unrecognized tax benefits, interest and penalties		2.5	3.1
Unrecognized tax benefit		2.2	$ 2.6	$ 2.2
Income tax examination, description			The Company and its U.S. subsidiaries remain open to examination by the IRS for years 2014 onwards under the statute of limitations. The Company’s subsidiaries in foreign tax jurisdictions are open to examination including France (2014 onwards), Germany (2015 onwards), Switzerland (2015 onwards) and the United Kingdom (2016 onwards).
Italian Tax Authorities [Member]
Income Tax Contingency [Line Items]
Unrecognized tax benefit	0.4	0.5
Income tax interest expense	$ 0.1	$ 0.2
France [Member]
Income Tax Contingency [Line Items]
Open tax year			2014
Germany [Member]
Income Tax Contingency [Line Items]
Open tax year			2015
Switzerland [Member]
Income Tax Contingency [Line Items]
Open tax year			2015
United Kingdom [Member]
Income Tax Contingency [Line Items]
Open tax year			2016
Italy [Member] | Earliest Tax Year [Member]
Income Tax Contingency [Line Items]
Open tax year			2011
Italy [Member] | Latest Tax Year [Member]
Income Tax Contingency [Line Items]
Open tax year			2013

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A brief description of status of the tax examination, significant findings to date, and the entity's position with respect to the findings.

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Tax year that remains open to examination under enacted tax laws, in CCYY format.

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Amount accrued for interest on an underpayment of income taxes and penalties related to a tax position claimed or expected to be claimed in the tax return.

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