Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Millions	Jun. 30, 2018	Dec. 31, 2017
Statement of Financial Position [Abstract]
Accounts receivable allowances	$ 3.8	$ 4.0
Common stock par value (in dollars per share)	$ 0.01	$ 0.01
Common stock shares authorized (in shares)	300,000,000	300,000,000
Common stock shares issued (in shares)	140,097,126	139,491,860
Common stock shares outstanding (in shares)	140,097,126	139,440,470
Treasury stock (in shares)	52,617	51,390