Income Taxes - Additional Information (Detail) - USD ($) $ in Millions	3 Months Ended		12 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017
Income Tax Contingency [Line Items]
Effective tax rates	21.20%	27.20%
Unrecognized tax benefits	$ 6.2
Unrecognized tax benefits that would affect the effective tax rate, if recognized	$ 0.6
Effective income tax rate reconciliation, tax cuts and jobs act, percent	21.00%
Tax cuts and jobs act, transition tax for accumulated foreign earnings, income tax expense				$ 81.8
Scenario, Forecast
Income Tax Contingency [Line Items]
Effective tax rates			22.00%
Earliest Tax Year | U.S. federal
Income Tax Contingency [Line Items]
Income tax examinations, years under examination	2015
Latest Tax Year | U.S. federal
Income Tax Contingency [Line Items]
Income tax examinations, years under examination	2017
State and local | Earliest Tax Year
Income Tax Contingency [Line Items]
Income tax examinations, years under examination	2001
State and local | Latest Tax Year
Income Tax Contingency [Line Items]
Income tax examinations, years under examination	2017
Non-U.S. | Earliest Tax Year
Income Tax Contingency [Line Items]
Income tax examinations, years under examination	2009
Non-U.S. | Latest Tax Year
Income Tax Contingency [Line Items]
Income tax examinations, years under examination	2017