Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Millions	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Allowance for doubtful accounts	$ 28.2	$ 33.8	$ 25.0
Preferred stock, par value (in dollars per shares)	$ 0.01	$ 0.01
Preferred stock, shares authorized	500,000	500,000
Preferred stock, shares issued	0	0
Treasury stock, shares	1,400,000	800,000
Common Class A
Common stock, par value (in dollars per share)	$ 0.025	$ 0.025
Common stock, shares authorized	105,000,000	105,000,000
Common stock, shares issued	41,700,000	40,400,000
Treasury stock, shares	900,000	200,000
Common Class B
Common stock, par value (in dollars per share)	$ 0.025	$ 0.025
Common stock, shares authorized	80,000,000	80,000,000.0
Common stock, shares issued	13,500,000	13,500,000
Treasury stock, shares	0	0
Common Class C
Common stock, par value (in dollars per share)	$ 0.025	$ 0.025
Common stock, shares authorized	20,000,000.0	20,000,000
Common stock, shares issued	500,000	500,000
Treasury stock, shares	500,000	500,000