Fair Value of Assets and Liabilities (Details 2) (USD $) In Millions, unless otherwise specified	3 Months Ended	12 Months Ended
	Mar. 31, 2015	Dec. 31, 2014
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	$ (281)	$ (278)
Weighted average projected option cost (as a percent)	1.76%	1.76%
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)	2.20%	2.00%
Fixed income securities - non-binding broker quotes
Quantitative information about the significant unobservable inputs
Fair value	959	1,030
Municipal - not rated by third party credit rating agencies
Quantitative information about the significant unobservable inputs
Fair value	$ 138	$ 169