Income Taxes - Additional Information (Detail) - USD ($) $ in Millions	3 Months Ended		12 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017
Income Tax Disclosure [Abstract]
Initial analysis of tax law changes recorded net tax expense			$ 4.3
Provisional expense for Transition Tax			55.0
Revaluation of deferred tax assets and liabilities			50.7
Provisional benefit to net deferred taxes			24.6
Provisional transition tax on unrepatriated foreign earnings			51.8
Effective income tax rate (as a percent)	23.00%	27.60%
Unrecognized tax benefits if recognized that would affect effective tax rate	$ 6.9		4.4
Accrued interest related to uncertain tax positions	0.8		0.7
Accrued penalties related to uncertain tax positions	0.1		$ 0.1
Unrecognized tax benefits subject to change within the next 12 months	$ 5.2