Inventories, net - Additional Information (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Inventories, net additional information
Charges to cost of sales due to lower of cost or market value	$ 2.2	$ 8.1	$ 0.8
Inventory on consignment at customer locations	4.6	3.6
Inventory reserves
Inventories, net additional information
Increase in inventory reserves	0.3
Inventory reserves	$ 13.9	$ 14.2