Derivative Instruments (Changes in Estimated Fair Value Related to Embedded Derivatives) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Changes In Estimated Fair Value Related To Embedded Derivatives [Line Items]
Total investment related gains (losses), net	$ 22,318	$ (76,465)	$ 225,416	$ 66,149
Gain Loss On Investments Related To Change In Fair Value Of Derivatives Excluding Embedded Derivatives	14,689	(24,451)	48,313	(137,240)
Total benefits and expenses	2,484,773	2,188,120	7,474,991	7,175,795
Net income	157,996	137,955	492,956	273,878
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	56,812	(67,461)	212,888	70,514
Net income	13,353	(15,693)	49,394	19,842
Embedded Derivatives In Equity Indexed Annuities [Member]
Changes In Estimated Fair Value Related To Embedded Derivatives [Line Items]
Total benefits and expenses	(35,650)	28,379	(86,775)	(32,637)
Net income	(23,920)	6,622	(57,896)	(53,772)
Embedded Derivatives In Variable Annuity Contracts [Member]
Changes In Estimated Fair Value Related To Embedded Derivatives [Line Items]
Total investment related gains (losses), net	(47,479)	19,829	(76,323)	106,954
Net income	$ 26,542	$ 11,052	$ 6,388	$ 52,326