Derivative Instruments (Non Hedging Derivatives and Embedded Derivatives Effect on Income Statement) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013
Income Affect Of Non Hedging Derivatives [Line Items]
Total investment related gains (losses), net	$ 84,571	$ 94,371
Policy acquisition costs and other insurance expenses	(354,873)	(357,357)
Interest credited	(110,594)	(125,483)
Not Designated as Hedging Instrument
Income Affect Of Non Hedging Derivatives [Line Items]
Total investment related gains (losses), net	49,517	48,162
Not Designated as Hedging Instrument | Interest Rate Swaps
Income Affect Of Non Hedging Derivatives [Line Items]
Total investment related gains (losses), net	29,653	(22,265)
Not Designated as Hedging Instrument | Interest Rate Options
Income Affect Of Non Hedging Derivatives [Line Items]
Total investment related gains (losses), net	1,282	1,982
Not Designated as Hedging Instrument | Financial Futures
Income Affect Of Non Hedging Derivatives [Line Items]
Total investment related gains (losses), net	(1,584)	(6,881)
Not Designated as Hedging Instrument | Foreign Currency Forwards
Income Affect Of Non Hedging Derivatives [Line Items]
Total investment related gains (losses), net	1,154	(5,659)
Not Designated as Hedging Instrument | Consumer Price Index Swaps
Income Affect Of Non Hedging Derivatives [Line Items]
Total investment related gains (losses), net	352	(871)
Not Designated as Hedging Instrument | Credit Default Swaps
Income Affect Of Non Hedging Derivatives [Line Items]
Total investment related gains (losses), net	(2,114)	3,904
Not Designated as Hedging Instrument | Equity Options
Income Affect Of Non Hedging Derivatives [Line Items]
Total investment related gains (losses), net	(8,966)	(30,623)
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	77,241	90,257
Not Designated as Hedging Instrument | Embedded Derivatives In Indexed Annuity Products
Income Affect Of Non Hedging Derivatives [Line Items]
Interest credited	(23,840)	(32,996)
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	$ (23,661)	$ 51,314