Consolidated Balance Sheets Parenthetical (Parentheticals) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Statement of Financial Position [Abstract]
Allowance for doubtful accounts receivable	$ 38.1	$ 40.9
Accumulated depreciation	$ 4,564.0	$ 4,505.5
Common stock, par value	$ 10
Common stock, shares authorized	65,000,000
Common stock, shares outstanding	33,289,327	33,289,327