Fair Value of Assets and Liabilities (Details 2) (USD $) In Millions, unless otherwise specified	9 Months Ended	12 Months Ended
	Sep. 30, 2013	Dec. 31, 2012
ARS backed by student loans | Discounted cash flow model
Quantitative information about the significant unobservable inputs
Fair value	$ 100	$ 394
ARS backed by student loans | Minimum | Discounted cash flow model
Quantitative information about the significant unobservable inputs
Anticipated date liquidity will return to the market	36 months	18 months
Weighted average anticipated date liquidity will return to the market	37 months	31 months
ARS backed by student loans | Maximum | Discounted cash flow model
Quantitative information about the significant unobservable inputs
Anticipated date liquidity will return to the market	54 months	60 months
Weighted average anticipated date liquidity will return to the market	49 months	43 months
Derivatives embedded in life and annuity contracts - Equity-indexed and forward starting options | Stochastic cash flow model
Quantitative information about the significant unobservable inputs
Fair value	(205)	(419)
Weighted average projected option cost (as a percent)	1.72%	1.92%
Derivatives embedded in life and annuity contracts - Equity-indexed and forward starting options | Minimum | Stochastic cash flow model
Quantitative information about the significant unobservable inputs
Projected option cost (as a percent)	1.00%	1.00%
Derivatives embedded in life and annuity contracts - Equity-indexed and forward starting options | Maximum | Stochastic cash flow model
Quantitative information about the significant unobservable inputs
Projected option cost (as a percent)	2.00%	2.00%
Liabilities held for sale - Equity-indexed and forward starting options | Stochastic cash flow model
Quantitative information about the significant unobservable inputs
Fair value	(249)
Weighted average projected option cost (as a percent)	1.93%
Liabilities held for sale - Equity-indexed and forward starting options | Minimum | Stochastic cash flow model
Quantitative information about the significant unobservable inputs
Projected option cost (as a percent)	1.00%
Liabilities held for sale - Equity-indexed and forward starting options | Maximum | Stochastic cash flow model
Quantitative information about the significant unobservable inputs
Projected option cost (as a percent)	2.00%
Fixed income securities - non-binding broker quotes
Quantitative information about the significant unobservable inputs
Fair value	1,220	1,870
Fair value	345
Municipal - not rated by third party credit rating agencies
Quantitative information about the significant unobservable inputs
Fair value	$ 226	$ 395