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, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Income Affect Of Non Hedging Derivatives [Line Items]
Total investment related gains (losses), net	$ 22,318	$ (76,465)	$ 225,416	$ 66,149
Policy acquisition costs and other insurance expenses	(336,411)	(268,081)	(1,100,658)	(995,943)
Interest credited	(120,952)	(59,939)	(347,508)	(303,767)
Other revenues	78,879	70,734	267,195	235,650
Not Designated as Hedging Instrument
Income Affect Of Non Hedging Derivatives [Line Items]
Total investment related gains (losses), net	(11,629)	(43,704)	98,102	7,589
Not Designated as Hedging Instrument | Interest Rate Swaps
Income Affect Of Non Hedging Derivatives [Line Items]
Total investment related gains (losses), net	9,121	(8,221)	61,025	(68,900)
Not Designated as Hedging Instrument | Interest Rate Options
Income Affect Of Non Hedging Derivatives [Line Items]
Total investment related gains (losses), net	865	(2,374)	4,151	(8,373)
Not Designated as Hedging Instrument | Financial Futures
Income Affect Of Non Hedging Derivatives [Line Items]
Total investment related gains (losses), net	6,446	(1,140)	(2,822)	(7,306)
Not Designated as Hedging Instrument | Foreign Currency Forwards
Income Affect Of Non Hedging Derivatives [Line Items]
Total investment related gains (losses), net	(5,277)	629	(2,945)	(7,988)
Not Designated as Hedging Instrument | Consumer Price Index Swaps
Income Affect Of Non Hedging Derivatives [Line Items]
Total investment related gains (losses), net	(274)	(39)	193	(2,027)
Not Designated as Hedging Instrument | Credit Default Swaps
Income Affect Of Non Hedging Derivatives [Line Items]
Total investment related gains (losses), net	(1,389)	10,807	1,280	17,138
Not Designated as Hedging Instrument | Equity Options
Income Affect Of Non Hedging Derivatives [Line Items]
Total investment related gains (losses), net	1,018	(24,113)	(16,748)	(59,784)
Not Designated as Hedging Instrument | Longevity Swap [Member]
Income Affect Of Non Hedging Derivatives [Line Items]
Other revenues	4,499	0	4,499	0
Not Designated as Hedging Instrument | Mortality Swap [Member]
Income Affect Of Non Hedging Derivatives [Line Items]
Other revenues	(320)	0	(320)	0
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	56,811	(67,461)	212,887	70,514
Not Designated as Hedging Instrument | Embedded Derivatives In Indexed Annuity [Member]
Income Affect Of Non Hedging Derivatives [Line Items]
Interest credited	(35,650)	28,379	(86,775)	(32,637)
Not Designated as Hedging Instrument | Embedded Derivatives In Variable Annuity [Member]
Income Affect Of Non Hedging Derivatives [Line Items]
Total investment related gains (losses), net	$ (47,479)	$ 19,829	$ (76,323)	$ 106,952