Commitments, Contingencies and Uncertainties - Additional Information (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Commitments And Contingencies Disclosure [Abstract]
Rent expense	$ 21.1	$ 18.1	$ 17.9
Capital expenditures committed	146.3
Capital expenditures in accounts payable	11.2	5.9
Pro rata share of letters of credit outstanding	$ 1.8	$ 1.8