Derivative Investments (Statements of Earnings) (Details) (Not Designated as Hedging Instrument [Member], USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Gain or (Loss) Recognized in Income on Derivative	$ (864)	$ (3,505)	$ (1,705)
Equity Index Options [Member] | Investment Income [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Gain or (Loss) Recognized in Income on Derivative	68,616	225,899	27,147
Fixed-Index Products [Member] | Universal Life and Annuity Contract Interest [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Gain or (Loss) Recognized in Income on Derivative	$ (69,480)	$ (229,404)	$ (28,852)