CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (Parenthetical) - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017
Statement Of Cash Flows [Abstract]
Non cash retirement of assets related to lease finance obligations	$ 0.6	$ 5.9
Non cash extinguishment of related lease finance obligation	0.6	5.9
Equipment purchased and financed through capital lease obligations	6.8	9.9
Purchases of property, plant and equipment included in accounts payable	$ 3.7	$ 0.2