Investments and Derivative Instruments (Details Textual 1) (USD $)																									3 Months Ended
	Mar. 31, 2012	Dec. 31, 2011	Mar. 31, 2012 Contingent Capital Facility Put Option [Member]	Dec. 31, 2011 Contingent Capital Facility Put Option [Member]	Mar. 31, 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]	Mar. 31, 2012 Customized Diversified Portfolios [Member] Basket Credit Default Swaps [Member]	Dec. 31, 2011 Customized Diversified Portfolios [Member] Basket Credit Default Swaps [Member]	Mar. 31, 2012 International [Member]	Dec. 31, 2011 International [Member]	Mar. 31, 2012 International [Member] Macro Hedge Program [Member]	Dec. 31, 2011 International [Member] Macro Hedge Program [Member]	Mar. 31, 2012 International [Member] Long Hedge Position [Member]	Dec. 31, 2011 International [Member] Long Hedge Position [Member]	Mar. 31, 2012 Currency Options [Member] International [Member] Macro Hedge Program [Member]	Dec. 31, 2011 Currency Options [Member] International [Member] Macro Hedge Program [Member]	Mar. 31, 2012 Currency Forwards [Member] Net Hedge Position [Member] Macro Hedge Program [Member]	Dec. 31, 2011 Currency Forwards [Member] Net Hedge Position [Member] Macro Hedge Program [Member]	Mar. 31, 2012 Currency Forwards [Member] Long Hedge Position [Member] Macro Hedge Program [Member]	Dec. 31, 2011 Currency Forwards [Member] Long Hedge Position [Member] Macro Hedge Program [Member]	Mar. 31, 2012 Currency Forwards [Member] Short Hedge Position [Member] Macro Hedge Program [Member]	Dec. 31, 2011 Currency Forwards [Member] Short Hedge Position [Member] Macro Hedge Program [Member]	Mar. 31, 2012 Currency Forwards [Member] International [Member] Macro Hedge Program [Member]	Dec. 31, 2011 Currency Forwards [Member] International [Member] Macro Hedge Program [Member]	Mar. 31, 2012 3 Win Related Foreign Currency Swaps [Member] JAPAN [Member]	Mar. 31, 2011 3 Win Related Foreign Currency Swaps [Member] JAPAN [Member]	Mar. 31, 2012 Fixed annuity hedging instruments [Member] JAPAN [Member]	Mar. 31, 2011 Fixed annuity hedging instruments [Member] JAPAN [Member]
Derivative [Line Items]
Maximum aggregate principal amount of junior subordinated notes			$ 500,000,000
Associated liability adjusted for changes in spot rates through realized capital gain																									118,000,000	42,000,000	157,000,000	53,000,000
Notional Amount	151,155,000,000	141,436,000,000	500,000,000	500,000,000					37,200,000,000	32,300,000,000	45,215,000,000	33,726,000,000	41,200,000,000	33,000,000,000	10,135,000,000	7,357,000,000	4,700,000,000	7,200,000,000	8,700,000,000	7,900,000,000	4,000,000,000	700,000,000	12,713,000,000	8,622,000,000
Amount of standard market indices of diversified portfolios of corporate issuers					4,400,000,000	4,200,000,000
Amount of customized diversified portfolios of corporate issuers							$ 553,000,000	$ 553,000,000