Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Millions	Sep. 30, 2018	Dec. 31, 2017
Statement of Financial Position [Abstract]
Allowances, accounts and notes receivable	$ 6.1	$ 5.9
Accumulated depreciation	$ 772.9	$ 774.2
Preferred stock, par value (in dollars per share)	$ 0.01	$ 0.01
Preferred stock, shares authorized	25,000,000	25,000,000
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common stock, shares authorized	200,000,000	200,000,000
Common stock, shares issued	87,170,197	87,170,197
Treasury stock, shares	46,891,591	45,361,145