Condensed Consolidated Balance Sheets (Unaudited) (Parenthetical) - USD ($) $ in Millions	Jun. 30, 2018	Dec. 31, 2017
Statement Of Financial Position [Abstract]
Accounts Receivable, allowances (in dollars)	$ 11.1	$ 10.9
Preferred stock authorized (in shares)	3,500,000	3,500,000
Par value of preferred stock per share (in dollars per share)	$ 0.01	$ 0.01
Preferred stock outstanding (in shares)	0	0
Common stock, shares authorized (in shares)	75,000,000	75,000,000
Common stock, shares issued (in shares)	40,793,983	40,793,983
Common stock, shares outstanding (in shares)	35,536,412	35,273,864
Treasury stock (in shares)	5,257,571	5,520,119