Income Taxes - Additional Information (Detail) - USD ($) $ in Millions	3 Months Ended			6 Months Ended		12 Months Ended
	Jun. 30, 2018	Mar. 31, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017	Dec. 31, 2017
Income Tax Disclosure [Abstract]
Cash payments (net of refunds) for income taxes	$ 3.9		$ 11.6	$ 6.1	$ 12.9
Effective income tax rate	30.50%		41.10%	30.70%	41.50%
Income tax rate	21.00%					35.00%
Measurement period adjustment, decrease in transition tax liability		$ 0.4
One-time transition tax on foreign subsidiaries' untaxed accumulated earnings, state income tax benefit		$ 0.4