Derivative Instruments (Details 5) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2012	Mar. 31, 2011
Changes In Estimated Fair Value Related To Embedded Derivatives [Line Items]
Total investment related gains (losses), net	$ 43,520	$ 123,620
Total benefits and expenses	2,112,212	2,055,680
Net income	123,318	148,920
Embedded Derivatives In Modified Coinsurance Or Funds Withheld Arrangements [Member]
Changes In Estimated Fair Value Related To Embedded Derivatives [Line Items]
Total investment related gains (losses), net	(9,428)	90,535
Net income	1,933	19,183
Embedded Derivatives In Equity Indexed Annuities [Member]
Changes In Estimated Fair Value Related To Embedded Derivatives [Line Items]
Total benefits and expenses	(19,739)	(41,271)
Net income	13,870	(36,650)
Embedded Derivatives In Variable Annuity Contracts [Member]
Changes In Estimated Fair Value Related To Embedded Derivatives [Line Items]
Total investment related gains (losses), net	146,375	32,654
Net income	$ 15,082	$ 8,801