Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Millions	Jun. 30, 2022	Dec. 31, 2021
Current Assets:
Allowances, accounts and notes receivable	$ 12.2	$ 10.7
Accumulated depreciation	$ 906.6	$ 888.8
Stockholders' deficit:
Preferred stock, par value	$ 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	$ 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	51,743,384	50,536,125