CONDENSED CONSOLIDATED BALANCE SHEETS (Unaudited) (Parenthetical) - USD ($) $ in Millions	Jun. 30, 2018	Dec. 31, 2017
Current assets:
Accounts receivable, allowance for doubtful accounts	$ 19.4	$ 18.7
Property, plant and equipment, accumulated depreciation	$ 227.0	$ 203.8
Stockholders' equity:
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common stock, shares authorized (in shares)	1,000,000,000	1,000,000,000
Common stock, shares issued (in shares)	200,741,094	198,377,237
Treasury stock (in shares)	1,645,910	2,159,266