Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Statement of Financial Position [Abstract]
Fixed maturities, available-for-sale, amortized cost (in dollars)	$ 21,672,727	$ 20,007,462
Fixed maturities, held-for-trading, amortized cost (in dollars)	519,495	612,889
Mortgage loans on real estate, allowances (in dollars)	2,882	2,890
Short-term investments, available-for-sale, amortized cost (in dollars)	$ 303,988	$ 267,026
Preferred stock, par value (in dollars per share)	$ 1	$ 1
Preferred stock, shares authorized	50,000,000	50,000,000
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0
Common stock, par value (in dollars per share)	$ 1	$ 1
Common stock, shares authorized	50,000,000	50,000,000
Common stock, shares issued	7,292,708	7,232,986
Common stock, shares outstanding	7,292,708	7,232,986