Condensed Consolidated Balance Sheets (Parenthetical) (USD $) In Millions, except Share data, unless otherwise specified	Jun. 30, 2014	Dec. 31, 2013
Investments, fair value	$ 3,573.3	$ 3,481.8
Class A Ordinary Shares [Member]
Common stock, nominal value (in dollars per share)	$ 0.01	$ 0.01
Common stock, issued (in shares)	214,812,401	222,081,117
Common stock, outstanding (in shares)	214,812,401	222,081,117
Class B Ordinary Shares [Member]
Common stock, nominal value (in dollars per share)	$ 0.01	$ 0.01
Common stock, issued (in shares)	10,139,184	10,147,184
Common stock, outstanding (in shares)	10,139,184	10,147,184
Class C Ordinary Shares [Member]
Common stock, nominal value (in dollars per share)	$ 0.01	$ 0.01
Common stock, issued (in shares)	555,391,246	556,221,669
Common stock, outstanding (in shares)	555,391,246	556,221,669