Fair Value of Assets and Liabilities (Details 2) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Quantitative information about the significant unobservable inputs
Fair value	$ 57,839	$ 57,948
Derivatives embedded in life and annuity contracts - Equity-indexed and forward starting options | Stochastic cash flow model
Quantitative information about the significant unobservable inputs
Weighted average projected option cost (as a percent)	1.75%	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%	2.20%
Fixed income securities - non-binding broker quotes
Quantitative information about the significant unobservable inputs
Assets, fair value disclosure	$ 307	$ 625
Municipal - not rated by third party credit rating agencies
Quantitative information about the significant unobservable inputs
Assets, fair value disclosure	80	96
Significant unobservable inputs (Level 3)
Quantitative information about the significant unobservable inputs
Assets, fair value disclosure	762	1,036
Significant unobservable inputs (Level 3) | Derivatives embedded in life and annuity contracts - Equity-indexed and forward starting options | Stochastic cash flow model
Quantitative information about the significant unobservable inputs
Financial and Nonfinancial Liabilities, Fair Value Disclosure	(247)	(247)
Recurring | Significant unobservable inputs (Level 3)
Quantitative information about the significant unobservable inputs
Financial and Nonfinancial Liabilities, Fair Value Disclosure	(293)	(307)
Fair value	558	846
Assets, fair value disclosure	$ 738	$ 981