Condensed Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Statement of Financial Position [Abstract]
Fixed maturities, available-for-sale, amortized cost (in dollars)	$ 22,125,948	$ 21,672,727
Fixed maturities, held for trading, amortized cost (in dollars)	59,034	519,495
Mortgage loans on real estate, allowances (in dollars)	773	2,882
Short-term investments, available-for-sale, amortized cost (in dollars)	$ 823,071	$ 303,988
Preferred stock, par value (in dollars per share)	$ 1	$ 1
Preferred stock, number of shares authorized	50,000,000	50,000,000
Preferred stock, number of shares issued	0	0
Preferred stock, number of shares outstanding	0	0
Common stock, par value (in dollars per share)	$ 1	$ 1
Common stock, number of shares authorized	50,000,000	50,000,000
Common stock, number of shares issued	7,292,708	7,292,708
Common stock, number of shares outstanding	7,292,708	7,292,708