Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Statement of Financial Position [Abstract]
Amortized cost on fixed maturities trading investments	$ 2,804,275	$ 2,503,494
Cost - equity security trading investments	313,528	387,851
Cost - short-term investments	$ 185,353	$ 373,180
Common Stock
Common stock, no par value (in dollars per share)	$ 0	$ 0
Common stock, shares authorized (in shares)	70,000,000	70,000,000
Common stock, shares issued (in shares)	55,164,000	55,121,000
Common stock, shares outstanding (in shares)	55,164,000	55,121,000