Income Taxes - Additional Information (Detail) - USD ($) $ in Millions	3 Months Ended		12 Months Ended
	Mar. 31, 2018	Dec. 31, 2017	Dec. 31, 2017	Dec. 31, 2016
Income Tax Contingency [Line Items]
Accrued net interest and penalties	$ 0.2
Increase in unrecognized tax benefits			$ 0.2
Unrecognized tax benefits, income tax interest and penalties accrued	0.5	$ 0.3	0.3
Unrecognized tax benefits, interest and penalties	3.1	2.5	2.5
Unrecognized tax benefit	$ 2.6	2.2	2.2	$ 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 benefits, interest and penalties	$ 0.5
Unrecognized tax benefit		0.5	$ 0.5
Income tax interest expense	0.1	$ 0.2
Additional tax due	$ 0.4
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