Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Current assets:
Allowance for doubtful accounts	$ (10.7)	$ (9.9)
Stockholders' equity:
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common stock, shares authorized (in shares)	200,000,000	200,000,000
Common stock, shares issued (in shares)	35,367,264	35,367,264
Treasury stock, shares (in shares)	1,481,611	1,513,808