Commitments and Contingencies - Additional Information (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Loss Contingencies [Line Items]
Operating leases rent expense net	$ 26.4	$ 34.0	$ 26.9
Contractual obligations under agreements with non cancelable terms to purchase goods or services	772.1
Other assets
Loss Contingencies [Line Items]
Restricted cash associated with outstanding bank guarnatee	$ 1.5