Consolidated Balance Sheet (Parenthetical) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Statement of Financial Position [Abstract]
Trade accounts receivable, allowance (in dollars)	$ 13.3	$ 11.6
Properties and equipment, accumulated depreciation and amortization	$ 1,497.0	$ 1,482.8
Common stock issued, par value (in dollars per share)	$ 0.01	$ 0.01
Common stock issued, shares authorized	300,000,000	300,000,000
Common stock issued, shares outstanding	66,735,913	66,792,968
Treasury Stock, Shares	10,720,720	10,663,659