Consolidated Balance Sheets (unaudited) (Parenthetical) - USD ($) $ in Millions	Sep. 30, 2020	Dec. 31, 2019
Statement of Financial Position [Abstract]
Allowance for doubtful accounts	$ 3.1	$ 13.3
Accumulated depreciation	$ 1,509.9	$ 1,497.0
Common stock issued, par value (in dollars per share)	$ 0.01	$ 0.01
Common stock issued, shares authorized (in shares)	300,000,000	300,000,000
Common stock issued, shares outstanding (in shares)	66,190,280	66,735,913
Treasury stock, at cost (shares)	11,266,353	10,720,720