Condensed Consolidated Balance Sheets (Parentheticals) - USD ($) $ in Millions	Mar. 31, 2020	Dec. 31, 2019
Current assets:
Allowance for doubtful accounts	$ 13.8	$ 14.5
Stockholders' equity:
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common stock, shares authorized (in shares)	150,000,000	150,000,000
Common stock, shares issued (in shares)	52,910,228	52,702,551
Common stock, shares outstanding (in shares)	45,086,055	45,113,722
Treasury stock, shares (in shares)	7,824,173	7,588,829