Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Statement Of Financial Position [Abstract]
Accounts Receivable, allowances (in dollars)	$ 10.9	$ 11.1
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)	35,273,864	34,960,304
Treasury stock, shares (in shares)	5,520,119	5,833,679