Derivative Investments (Statements of Earnings) (Details) - Derivatives not designated as hedging instruments - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Gain or (Loss) Recognized in Income on Derivatives	$ (4,207)	$ 8,211	$ (6,625)	$ 7,032
Equity index options | Investment Income
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Gain or (Loss) Recognized in Income on Derivatives	32,215	2,094	93,421	(10,807)
Fixed-index products | Universal Life and Annuity Contract Interest
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Gain or (Loss) Recognized in Income on Derivatives	$ (36,422)	$ 6,117	$ (100,046)	$ 17,839