Consolidated Balance Sheets (Parenthetical) $ in Millions	Dec. 31, 2015 USD ($) shares	Dec. 31, 2014 USD ($) shares
Fixed maturity investments trading, amortized cost | $	$ 7,290.6	$ 6,035.2
Equity securities trading - cost | $	$ 395.3	$ 791.2
Common stock, shares issued	95,523,230	100,775,256
Common stock, shares outstanding	90,959,635	96,195,482
Treasury stock (shares)	4,563,595	4,579,774