Condensed Consolidated Balance Sheets (unaudited) (Parenthetical) - USD ($) $ in Millions	Sep. 30, 2020	Dec. 31, 2019
Other investments	$ 1,380.6	$ 1,289.2
Class A
Common stock, nominal value (in dollars per share)	$ 0.01	$ 0.01
Common stock, issued (in shares)	180,998,492	181,560,735
Common stock, outstanding (in shares)	180,998,492	181,560,735
Class B
Common stock, nominal value (in dollars per share)	$ 0.01	$ 0.01
Common stock, issued (in shares)	12,561,444	12,151,526
Common stock, outstanding (in shares)	12,561,444	12,151,526
Class C
Common stock, nominal value (in dollars per share)	$ 0.01	$ 0.01
Common stock, issued (in shares)	390,198,924	438,867,447
Common stock, outstanding (in shares)	390,198,924	438,867,447