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, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Changes In Estimated Fair Value Related To Embedded Derivatives [Line Items]
Total investment related gains (losses), net	$ (76,465)	$ 76,053	$ 66,149	$ 143,374
Total benefits and expenses	2,188,120	2,247,602	7,175,795	6,519,675
Net income	137,955	144,475	273,878	408,904
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	(67,461)	54,836	70,514	40,955
Net income	(15,693)	11,228	19,842	10,563
Embedded Derivatives In Equity Indexed Annuities [Member]
Changes In Estimated Fair Value Related To Embedded Derivatives [Line Items]
Total benefits and expenses	28,379	(33,821)	(32,637)	(26,422)
Net income	6,622	(22,529)	(53,772)	6,465
Embedded Derivatives In Variable Annuity Contracts [Member]
Changes In Estimated Fair Value Related To Embedded Derivatives [Line Items]
Total investment related gains (losses), net	19,829	2,579	106,952	74,025
Net income	$ 11,052	$ 1,588	$ 52,326	$ 494