Consolidated Balance Sheets (Parentheticals) - USD ($) shares in Millions, $ in Millions	Sep. 30, 2019	Dec. 31, 2018
Statement of Financial Position [Abstract]
Allowance for doubtful accounts	$ 9.1	$ 7.0
Preferred stock, par value (in dollars per share)	$ 0.01	$ 0.01
Preferred stock, authorized (in shares)	100.0	100.0
Preferred stock, issued (in shares)	0.0	0.0
Preferred stock, outstanding (in shares)	0.0	0.0
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common stock, shares authorized (in shares)	1,000.0	1,000.0
Common stock, shares issued (in shares)	143.9	147.7
Common stock, shares outstanding (in shares)	143.9	147.7