Commitments and Contingencies - Additional Information (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Commitments and Contingencies Disclosure [Abstract]
Operating lease rent expense	$ 52.0	$ 46.5	$ 44.7
Noncancelable commitments for capital expenditure in 2018	$ 24.0