Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Mar. 31, 2016	Dec. 31, 2015
Fixed income securities, amortized cost	$ 5,539,759	$ 4,992,756
Fixed income securities pledged as collateral, amortized cost	64,667	64,612
Short-term investments, amortized cost	436,759	225,789
Other investments	$ 294,376	$ 285,261
Preferred stock, par value	$ 0.01	$ 0.01
Preferred stock, shares authorized	20,000,000	20,000,000
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0
Common stock, par value	$ 0.01	$ 0.01
Common stock, shares authorized	130,000,000	130,000,000
Common stock, shares issued	45,047,686	45,044,222
Common stock, shares outstanding	45,047,686	45,044,222
Treasury stock, shares	690	8,202