Derivative Instruments (Details 6) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011
Income Affect Of Non Hedging Derivatives [Line Items]
Total investment related gains (losses), net	$ 23,801	$ 27,388	$ 67,321	$ 151,008
Policy Acquisition Costs And Other Insurance Expenses	335,939	274,519	643,573	620,766
Interest credited	66,697	96,196	154,739	202,259
Interest Rate Swap Member
Income Affect Of Non Hedging Derivatives [Line Items]
Total investment related gains (losses), net	73,342	25,343	25,990	14,613
Future Member
Income Affect Of Non Hedging Derivatives [Line Items]
Total investment related gains (losses), net	11,074	(2,873)	(6,335)	(14,296)
Foreign Exchange Forward Member
Income Affect Of Non Hedging Derivatives [Line Items]
Total investment related gains (losses), net	516	595	(1,093)	(260)
Consumer Price Index Swap [Member]
Income Affect Of Non Hedging Derivatives [Line Items]
Total investment related gains (losses), net	(1,431)	503	(2,233)	1,315
Credit Default Swap Member
Income Affect Of Non Hedging Derivatives [Line Items]
Total investment related gains (losses), net	(4,795)	988	7,019	1,880
Equity Member
Income Affect Of Non Hedging Derivatives [Line Items]
Total investment related gains (losses), net	3,367	3,919	(34,616)	(650)
Embedded Derivatives In Modified Coinsurance Or Funds Withheld Arrangements [Member]
Income Affect Of Non Hedging Derivatives [Line Items]
Total investment related gains (losses), net	(4,453)	10,525	(13,881)	101,060
Embedded Derivatives In Indexed Annuity [Member]
Income Affect Of Non Hedging Derivatives [Line Items]
Policy Acquisition Costs And Other Insurance Expenses	859	4,026	(139)	12,119
Interest credited	26,279	(36,101)	7,538	(85,466)
Embedded Derivatives In Variable Annuity [Member]
Income Affect Of Non Hedging Derivatives [Line Items]
Total investment related gains (losses), net	$ (74,929)	$ (25,860)	$ 71,446	$ 6,794