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Consolidated Balance Sheets (Parenthetical) - USD ($)
$ in Millions
Dec. 31, 2020
Dec. 31, 2019
Statement of Financial Position [Abstract]    
Accounts receivable - trade, allowance for doubtful accounts $ 0.1 $ 1.2
Accumulated depreciation and amortization $ 1,191.4 $ 1,079.2
Stockholders' Equity    
Preferred stock par value (in dollars per share)   $ 0.01
Preferred stock shares authorized (in shares) 20,000,000 20,000,000
Preferred stock shares outstanding (in shares) 0 0
Common stock par value (in dollars per share) $ 0.01 $ 0.01
Common stock shares authorized (in shares) 200,000,000 200,000,000
Common stock shares issued (in shares) 46,767,164 46,767,164
Treasury stock (in shares) 19,518,551 16,307,048