Fair Value of Assets and Liabilities - Quantitative information about Level 3 instruments (Details) $ in Millions	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)
Quantitative information about the significant unobservable inputs
Fixed income securities	$ 57,170	$ 58,992
Fixed income securities - non-binding broker quotes
Quantitative information about the significant unobservable inputs
Assets, fair value disclosure	105	271
Municipal - not rated by third party credit rating agencies
Quantitative information about the significant unobservable inputs
Assets, fair value disclosure	44	58
Significant unobservable inputs (Level 3)
Quantitative information about the significant unobservable inputs
Assets, fair value disclosure	697	840
Recurring \| Significant unobservable inputs (Level 3)
Quantitative information about the significant unobservable inputs
Fixed income securities	325	606
Assets, fair value disclosure		837
Derivatives embedded in life and annuity contracts - Equity-indexed and forward starting options \| Significant unobservable inputs (Level 3)
Quantitative information about the significant unobservable inputs
Fair value	$ (185)	$ (252)
Projected option cost \| Derivatives embedded in life and annuity contracts - Equity-indexed and forward starting options \| Significant unobservable inputs (Level 3) \| Weighted Average
Quantitative information about the significant unobservable inputs
Embedded Derivative Asset (Liability) Net, Measurement Input	0.0174	0.0174
Projected option cost \| Derivatives embedded in life and annuity contracts - Equity-indexed and forward starting options \| Significant unobservable inputs (Level 3) \| Minimum
Quantitative information about the significant unobservable inputs
Embedded Derivative Asset (Liability) Net, Measurement Input	0.010	0.010
Projected option cost \| Derivatives embedded in life and annuity contracts - Equity-indexed and forward starting options \| Significant unobservable inputs (Level 3) \| Maximum
Quantitative information about the significant unobservable inputs
Embedded Derivative Asset (Liability) Net, Measurement Input	0.022	0.022

Fair value portion of probable future economic benefits obtained or controlled by an entity as a result of past transactions or events.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
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-Section 50
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Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 45
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Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
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