v3.10.0.1
Condensed Consolidated Balance Sheets (unaudited) (Parenthetical) - USD ($)
$ in Millions
Jun. 30, 2018
Dec. 31, 2017
Investments $ 2,164.1 $ 2,315.3
Class A    
Common stock, nominal value (in dollars per share) $ 0.01 $ 0.01
Common stock, issued (in shares) 207,403,209 219,668,579
Common stock, outstanding (in shares) 207,403,209 219,668,579
Class B    
Common stock, nominal value (in dollars per share) $ 0.01 $ 0.01
Common stock, issued (in shares) 11,102,619 11,102,619
Common stock, outstanding (in shares) 11,102,619 11,102,619
Class C    
Common stock, nominal value (in dollars per share) $ 0.01 $ 0.01
Common stock, issued (in shares) 555,820,059 584,332,055
Common stock, outstanding (in shares) 555,820,059 584,332,055