Fair Value of Assets and Liabilities (Details 2) (USD $) In Millions, unless otherwise specified	6 Months Ended
	Jun. 30, 2012
ARS backed by student loans | Discounted cash flow model
Quantitative information about the significant unobservable inputs
Fair value	604
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	60 months
ARS backed by student loans | Maximum | Weighted average | Discounted cash flow model
Quantitative information about the significant unobservable inputs
Anticipated date liquidity will return to the market	45 months
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	18 months
ARS backed by student loans | Minimum | Weighted average | Discounted cash flow model
Quantitative information about the significant unobservable inputs
Anticipated date liquidity will return to the market	33 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	(551)
Derivatives embedded in life and annuity contracts - Equity-indexed and forward starting options | Weighted average | Stochastic cash flow model
Quantitative information about the significant unobservable inputs
Projected option cost (as a percent)	3.35%
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)	3.50%
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)	1.50%
Municipal - not rated by third party credit rating agencies
Quantitative information about the significant unobservable inputs
Fair value	414
Fixed income securities - non-binding broker quotes
Quantitative information about the significant unobservable inputs
Fair value	1,780