Derivative Instruments (Changes in Estimated Fair Value Related to Embedded Derivatives) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Changes In Estimated Fair Value Related To Embedded Derivatives [Line Items]
Total investment related gains (losses), net	$ (111,346)	$ 22,318	$ (119,941)	$ 225,416
Gain Loss On Investments Related To Change In Fair Value Of Derivatives Excluding Embedded Derivatives	67,831	14,689	42,224	48,313
Total benefits and expenses	2,298,497	2,484,773	7,051,535	7,474,991
Net income	83,534	157,996	339,039	492,956
Embedded Derivatives In Modified Coinsurance Or Funds Withheld Arrangements
Changes In Estimated Fair Value Related To Embedded Derivatives [Line Items]
Total investment related gains (losses), net	(46,169)	56,812	(71,592)	212,888
Net income	(11,783)	13,353	(18,287)	49,394
Embedded Derivatives In Equity Indexed Annuities [Member]
Changes In Estimated Fair Value Related To Embedded Derivatives [Line Items]
Total benefits and expenses	50,246	(35,650)	28,999	(86,775)
Net income	27,861	(23,920)	13,095	(57,896)
Embedded Derivatives In Variable Annuity Contracts [Member]
Changes In Estimated Fair Value Related To Embedded Derivatives [Line Items]
Total investment related gains (losses), net	(95,372)	(47,479)	(69,628)	(76,323)
Net income	$ (116,994)	$ 26,542	$ (106,796)	$ 6,388