Consolidated Statements of Financial Position (Parenthetical) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Statement of Financial Position [Abstract]
Fixed maturities, available-for-sale, amortized cost	$ 4,941,944	$ 5,552,911
Equity securities, available-for-sale, cost	$ 20,754	$ 16,390
Common stock, par value (in dollars per share)	$ 10	$ 10
Common stock, shares authorized	1,000,000	1,000,000
Common stock, shares issued	250,000	250,000
Common stock, shares outstanding	250,000	250,000