Unaudited Condensed Consolidated Balance Sheets (Parenthetical) $ in Millions	Mar. 31, 2016 USD ($) shares	Dec. 31, 2015 USD ($) shares
Fixed maturity investments trading, amortized cost | $	$ 7,595.1	$ 7,290.6
Equity securities trading, cost | $	$ 209.4	$ 395.3
Common stock, shares issued	94,062,342	95,523,230
Common stock, shares outstanding	89,840,448	90,959,635
Treasury stock (shares)	4,221,894	4,563,595