Condensed Consolidated Balance Sheets (Parentheticals) - USD ($) $ in Millions	Sep. 30, 2017	Dec. 31, 2016
Current assets:
Allowance for doubtful accounts	$ 7.1	$ 7.1
Stockholders' equity:
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common stock, shares authorized (in shares)	100,000,000	100,000,000
Common stock, shares issued (in shares)	52,397,668	52,227,511
Common stock, shares outstanding (in shares)	46,191,446	46,152,958
Treasury stock, shares (in shares)	6,206,222	6,074,553