Investments and Derivative Instruments (Details Textual 1) (USD $)																			3 Months Ended		9 Months Ended		3 Months Ended		9 Months Ended
	Sep. 30, 2012	Dec. 31, 2011	Sep. 30, 2012 International Program Hedging Instruments [Member]	Dec. 31, 2011 International Program Hedging Instruments [Member]	Sep. 30, 2012 Contingent Capital Facility Put Option [Member]	Dec. 31, 2011 Contingent Capital Facility Put Option [Member]	Sep. 30, 2012 Standard Market Indices of Diversified Portfolios [Member] Basket Credit Default Swaps [Member]	Dec. 31, 2011 Standard Market Indices of Diversified Portfolios [Member] Basket Credit Default Swaps [Member]	Sep. 30, 2012 Customized Diversified Portfolios [Member] Basket Credit Default Swaps [Member]	Dec. 31, 2011 Customized Diversified Portfolios [Member] Basket Credit Default Swaps [Member]	Sep. 30, 2012 International [Member]	Dec. 31, 2011 International [Member]	Sep. 30, 2012 International [Member] Long Hedge Position [Member]	Dec. 31, 2011 International [Member] Long Hedge Position [Member]	Sep. 30, 2012 Currency Options [Member] International Program Hedging Instruments [Member]	Dec. 31, 2011 Currency Options [Member] International Program Hedging Instruments [Member]	Sep. 30, 2012 Currency Forwards [Member] Short Hedge Position [Member]	Dec. 31, 2011 Currency Forwards [Member] Short Hedge Position [Member]	Sep. 30, 2012 3 Win Related Foreign Currency Swaps [Member] JAPAN	Sep. 30, 2011 3 Win Related Foreign Currency Swaps [Member] JAPAN	Sep. 30, 2012 3 Win Related Foreign Currency Swaps [Member] JAPAN	Sep. 30, 2011 3 Win Related Foreign Currency Swaps [Member] JAPAN	Sep. 30, 2012 Japanese fixed annuity hedging instruments [Member] JAPAN	Sep. 30, 2011 Japanese fixed annuity hedging instruments [Member] JAPAN	Sep. 30, 2012 Japanese fixed annuity hedging instruments [Member] JAPAN	Sep. 30, 2011 Japanese fixed annuity hedging instruments [Member] JAPAN	Sep. 30, 2012 Foreign Exchange Forward [Member] International Program Hedging Instruments [Member]		Dec. 31, 2011 Foreign Exchange Forward [Member] International Program Hedging Instruments [Member]		Sep. 30, 2012 Foreign Exchange Forward [Member] Net Hedge Position [Member] International Program Hedging Instruments [Member]	Dec. 31, 2011 Foreign Exchange Forward [Member] Net Hedge Position [Member] International Program Hedging Instruments [Member]	Sep. 30, 2012 Foreign Exchange Forward [Member] Long Hedge Position [Member] International Program Hedging Instruments [Member]	Dec. 31, 2011 Foreign Exchange Forward [Member] Long Hedge Position [Member] International Program Hedging Instruments [Member]	Sep. 30, 2012 Foreign Exchange Forward [Member] Short Hedge Position [Member] International Program Hedging Instruments [Member]	Dec. 31, 2011 Foreign Exchange Forward [Member] Short Hedge Position [Member] International Program Hedging Instruments [Member]
Derivative [Line Items]
Maximum aggregate principal amount of junior subordinated notes					$ 500
Associated liability adjusted for changes in spot rates through realized capital gain																			(46,000,000)	(93,000,000)	19,000,000	(100,000,000)	(54,000,000)	(115,000,000)	33,000,000	(125,000,000)
Notional Amount	173,376,000,000	141,436,000,000	67,294,000,000	33,726,000,000	500,000,000	500,000,000					62,300,000,000	33,000,000,000	5,000,000,000	700,000,000	9,708,000,000	7,357,000,000	57,300,000,000	32,300,000,000									10,148,000,000	[1]	8,622,000,000	[1]	1,900,000,000	7,200,000,000	6,000,000,000	7,900,000,000	4,100,000,000	700,000,000
Amount of standard market indices of diversified portfolios of corporate issuers							5,000,000,000	4,200,000,000
Amount of customized diversified portfolios of corporate issuers									$ 353,000,000	$ 533,000,000

[1] As of September 30, 2012 and December 31, 2011 net notional amounts are $1.9 billion and $7.2 billion, respectively, which include $6.0 billion and $7.9 billion, respectively, related to long positions and $4.1 billion and $0.7 billion, respectively, related to short positions.