Fair Value Measurements (Details Textual) (USD $)	3 Months Ended				3 Months Ended
	Mar. 31, 2012	Dec. 31, 2011	Mar. 31, 2012 Credit-linked notes [Member]	Dec. 31, 2011 Credit-linked notes [Member]	Mar. 31, 2012 Maximum [Member]	Mar. 31, 2012 Minimum [Member]	Mar. 31, 2012 Credit standing adjustment assumption net of reinsurance [Member]	Mar. 31, 2011 Credit standing adjustment assumption net of reinsurance [Member]	Mar. 31, 2012 Outperformance (underperformance) of the underlying actively managed fund compared to indices [Member]	Mar. 31, 2011 Outperformance (underperformance) of the underlying actively managed fund compared to indices [Member]
Derivative [Line Items]
Pre-tax realized gains							$ (49,000,000)	$ (1,000,000)	$ 13,000,000	$ 25,000,000
Daily analyses identify price					5.00%	3.00%
Percentage difference of sale trade price from prior days price						3.00%
Percentage difference of purchase trade price from current days price						3.00%
Percentage difference of weekly analyses identify price from published bond						5.00%
Percentage change of monthly analyses identify price						3.00%
Debt Instrument [Line Items]
Outstanding principal balance of notes			243,000,000	243,000,000
Fair Value Measurements - Financial Instruments Excluding Guaranteed Living Benefits (Textual) [Abstract]
Transfer of amount from level 1 to 2	138,000,000
Transfer of amount from level 2 to 1	0
Cash collateral liability	97,000,000,000	1,400,000,000
Investment sales receivable	4,300,000,000	4,000,000,000
Derivatives priced by valuation models	98.00%	98.00%
Credit standing adjustment	31,000,000	80,000,000
Behavior Risk Margin	$ 355,000,000	$ 419,000,000