Consolidated Balance Sheets (Parenthetical) - USD ($) shares in Millions, $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Consolidated Balance Sheets
Accounts receivable, allowance for doubtful accounts	$ 33.6	$ 33.5
Class A Common Stock, par value (in dollars per share)	$ 0.001	$ 0.001
Class A Common Stock, shares authorized	1,000.0	1,000.0
Class A Common Stock, shares issued	298.7	299.2
Class A Common Stock, shares outstanding	297.9	298.5
Treasury stock, shares	0.8	0.7