Derivative Instruments (Non Hedging Derivatives and Embedded Derivatives Effect on Income Statement) (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
Income Affect Of Non Hedging Derivatives [Line Items]
Total investment related gains (losses), net	$ (76,465)	$ 76,053	$ 66,149	$ 143,374
Policy acquisition costs and other insurance expenses	(268,081)	(318,106)	(995,943)	(961,679)
Interest credited	(59,939)	(130,341)	(303,767)	(285,080)
Not Designated as Hedging Instrument
Income Affect Of Non Hedging Derivatives [Line Items]
Total investment related gains (losses), net	(43,704)	3,022	7,589	56,717
Not Designated as Hedging Instrument | Interest Rate Swaps
Income Affect Of Non Hedging Derivatives [Line Items]
Total investment related gains (losses), net	(8,221)	(1,437)	(68,900)	24,553
Not Designated as Hedging Instrument | Interest Rate Options
Income Affect Of Non Hedging Derivatives [Line Items]
Total investment related gains (losses), net	(2,374)	0	(8,373)	0
Not Designated as Hedging Instrument | Financial Futures
Income Affect Of Non Hedging Derivatives [Line Items]
Total investment related gains (losses), net	(1,140)	(3,977)	(7,306)	(10,312)
Not Designated as Hedging Instrument | Foreign Currency Forwards
Income Affect Of Non Hedging Derivatives [Line Items]
Total investment related gains (losses), net	629	519	(7,988)	(574)
Not Designated as Hedging Instrument | Consumer Price Index Swaps
Income Affect Of Non Hedging Derivatives [Line Items]
Total investment related gains (losses), net	(39)	422	(2,027)	(1,811)
Not Designated as Hedging Instrument | Credit Default Swaps
Income Affect Of Non Hedging Derivatives [Line Items]
Total investment related gains (losses), net	10,807	7,817	17,138	14,835
Not Designated as Hedging Instrument | Equity Options
Income Affect Of Non Hedging Derivatives [Line Items]
Total investment related gains (losses), net	(24,113)	(23,916)	(59,784)	(58,532)
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	(67,461)	54,836	70,514	40,955
Not Designated as Hedging Instrument | Embedded Derivatives In Indexed Annuity Products
Income Affect Of Non Hedging Derivatives [Line Items]
Policy acquisition costs and other insurance expenses	0	(224)	0	(363)
Interest credited	28,379	(33,597)	(32,637)	(26,059)
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	$ 19,829	$ 2,579	$ 106,952	$ 74,025