Unaudited Interim Statements of Financial Position (Parenthetical) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Statement of Financial Position [Abstract]
Fixed Maturities, Available-for-sale, Amortized Cost	$ 14,517,513	$ 12,465,746
Fixed Maturities, Available-for-sale, allowance for credit losses	982
Fixed maturities, trading, amortized cost	525,032	349,428
Equity securities, at cost	66,470	63,647
Commercial mortgage and other loans, allowance for credit losses	6,879	2,663
Other invested assets, at fair value	$ 13,524	$ 10,492
Common stock, par value (in dollars per share)	$ 100	$ 100
Common stock, shares authorized	25,000	25,000
Common stock, shares issued	25,000	25,000
Common stock, shares outstanding	25,000	25,000