Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Statement Of Financial Position [Abstract]
Property, plant and equipment, accumulated depreciation and amortization	$ 412.9	$ 361.4
Common stock, par value	$ 0.01	$ 0.01
Common stock, shares authorized	200,000,000	200,000,000
Common stock, shares issued	61,553,724	60,782,736
Common stock, shares outstanding	48,808,239	52,772,139
Treasury stock, shares	12,745,485	8,010,597