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	$ 24,222	$ 24,629
Significant unobservable inputs (Level 3)
Quantitative information about the significant unobservable inputs
Fair value	(292)	(307)
Assets at fair value	526	736
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
Fair value	$ (246)	$ (247)
Weighted average projected option cost (as a percent)	1.75%	1.76%
Significant unobservable inputs (Level 3) | 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%
Significant unobservable inputs (Level 3) | 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%
Recurring basis | Significant unobservable inputs (Level 3)
Quantitative information about the significant unobservable inputs
Fair value	$ 439	$ 666
Assets at fair value	517	728
Non-recurring basis | Significant unobservable inputs (Level 3)
Quantitative information about the significant unobservable inputs
Assets at fair value	9	8
Non-recurring basis | Significant unobservable inputs (Level 3) | Fixed income securities - non-binding broker quotes
Quantitative information about the significant unobservable inputs
Assets at fair value	$ 296	$ 577