Derivative Instruments (Non Hedging Derivatives and Embedded Derivatives Effect on Income Statement) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Income Affect Of Non Hedging Derivatives [Line Items]
Total investment related gains (losses), net	$ 118,527	$ 48,243	$ 203,098	$ 142,614
Policy acquisition costs and other insurance expenses	(409,374)	(370,505)	(764,247)	(727,862)
Interest credited	(115,962)	(118,345)	(226,556)	(243,828)
Not Designated as Hedging Instrument
Income Affect Of Non Hedging Derivatives [Line Items]
Total investment related gains (losses), net	60,213	3,128	109,732	51,293
Not Designated as Hedging Instrument | Interest Rate Swaps
Income Affect Of Non Hedging Derivatives [Line Items]
Total investment related gains (losses), net	22,251	(38,415)	51,904	(60,679)
Not Designated as Hedging Instrument | Interest Rate Options
Income Affect Of Non Hedging Derivatives [Line Items]
Total investment related gains (losses), net	2,004	(7,981)	3,286	(5,998)
Not Designated as Hedging Instrument | Financial Futures
Income Affect Of Non Hedging Derivatives [Line Items]
Total investment related gains (losses), net	(7,684)	714	(9,268)	(6,167)
Not Designated as Hedging Instrument | Foreign Currency Forwards
Income Affect Of Non Hedging Derivatives [Line Items]
Total investment related gains (losses), net	1,178	(2,958)	2,332	(8,617)
Not Designated as Hedging Instrument | Consumer Price Index Swaps
Income Affect Of Non Hedging Derivatives [Line Items]
Total investment related gains (losses), net	114	(1,117)	467	(1,988)
Not Designated as Hedging Instrument | Credit Default Swaps
Income Affect Of Non Hedging Derivatives [Line Items]
Total investment related gains (losses), net	4,783	2,427	2,669	6,332
Not Designated as Hedging Instrument | Equity Options
Income Affect Of Non Hedging Derivatives [Line Items]
Total investment related gains (losses), net	(8,800)	(5,049)	(17,765)	(35,672)
Not Designated as Hedging Instrument | Embedded Derivatives In Modified Coinsurance Or Funds Withheld Arrangements
Income Affect Of Non Hedging Derivatives [Line Items]
Total investment related gains (losses), net	78,835	47,717	156,076	137,974
Not Designated as Hedging Instrument | Embedded Derivatives In Indexed Annuity Products
Income Affect Of Non Hedging Derivatives [Line Items]
Interest credited	(27,285)	(28,019)	(51,125)	(61,015)
Not Designated as Hedging Instrument | Embedded Derivatives In Variable Annuity Products
Income Affect Of Non Hedging Derivatives [Line Items]
Total investment related gains (losses), net	$ (5,183)	$ 35,809	$ (28,844)	$ 87,123