Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Jun. 30, 2015	Dec. 31, 2014
Statement of Financial Position [Abstract]
Fixed maturities, available for sale, amortized cost	$ 13,126,918	$ 12,823,612
Equity securities, cost	776	776
Long-term debt, fair value	$ 868,801	$ 1,148,749
Preferred stock, par value (in dollars per share)	$ 1	$ 1
Preferred stock, shares authorized	5,000,000	5,000,000
Preferred stock, shares outstanding	0	0
Common stock, par value	$ 1	$ 1
Common stock, shares authorized	320,000,000	320,000,000
Common stock, shares issued	134,218,183	134,218,183
Common stock, shares held in treasury	8,976,671	6,287,907