Condensed Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Millions	Jun. 30, 2018	Dec. 31, 2017
Statement Of Financial Position [Abstract]
Property, plant and equipment, accumulated depreciation and amortization	$ 396.0	$ 361.4
Common stock, par value	$ 0.01	$ 0.01
Common stock, shares authorized	200,000,000	200,000,000
Common stock, shares issued	61,434,462	60,782,736
Common stock, shares outstanding	51,638,049	52,772,139
Treasury stock, shares	9,796,413	8,010,597