Fair Value of Assets and Liabilities (Level 3 Fair Value Measurment) (Details) (Significant unobservable inputs (Level 3), USD $) In Millions, unless otherwise specified	3 Months Ended	12 Months Ended
	Mar. 31, 2015	Dec. 31, 2014
Quantitative information about the significant unobservable inputs
Fair value	$ 1,003	$ 1,077
Fixed Income Securities Valued Based on Nonbinding Broker Quotes [Member]
Quantitative information about the significant unobservable inputs
Fair value	856	914
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%