CONSOLIDATED BALANCE SHEET (Parenthetical) - USD ($) $ in Millions	Sep. 30, 2018	Dec. 31, 2017
Current assets
Trade receivables, allowance (in dollars)	$ 15.9	$ 16.2
Stockholders’ equity
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common authorized (in shares)	300,000,000	300,000,000.0
Common issued (in shares)	131,200,000	130,400,000
Treasury stock (in shares)	58,200,000	50,200,000