Net Property, Plant and Equipment - Additional Information (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Net Property, Plant and Equipment
Depreciation expense related to property, plant and equipment	$ 103.5	$ 93.3	$ 76.4
Construction in progress
Net Property, Plant and Equipment
Capitalized interest	$ 3.1	$ 1.9