Condensed Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Millions	Jun. 30, 2015	Dec. 31, 2014
Investments, fair value	$ 1,928.8	$ 1,662.7
Class A Ordinary Shares [Member]
Common stock, nominal value (in dollars per share)	$ 0.01	$ 0.01
Common stock, issued (in shares)	252,505,774	251,167,686
Common stock, outstanding (in shares)	252,505,774	251,167,686
Class B Ordinary Shares [Member]
Common stock, nominal value (in dollars per share)	$ 0.01	$ 0.01
Common stock, issued (in shares)	10,472,517	10,139,184
Common stock, outstanding (in shares)	10,472,517	10,139,184
Class C Ordinary Shares [Member]
Common stock, nominal value (in dollars per share)	$ 0.01	$ 0.01
Common stock, issued (in shares)	614,457,550	630,353,372
Common stock, outstanding (in shares)	614,457,550	630,353,372