Consolidated Balance Sheets (unaudited) (Parenthetical) - USD ($) $ in Millions	Jun. 30, 2017	Dec. 31, 2016
Statement of Financial Position [Abstract]
Trade accounts receivable, allowance	$ 5.3	$ 4.5
Common stock issued, par value (in usd per share)	$ 0.01	$ 0.01
Common stock, number of shares authorized	300,000,000	300,000,000
Common stock, number of shares outstanding	71,607,293	71,081,764