Fair Value of Assets and Liabilities Fair Value of Assets and Liabilities (Quantitative Information for Level 3 Inputs) (Details) $ in Millions	Mar. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)
Fair Value, Option, Quantitative Disclosures [Line Items]
Assets, Fair Value Disclosure	$ 50,258	$ 52,245
Asset-backed Securities [Member]
Fair Value, Option, Quantitative Disclosures [Line Items]
Assets, Fair Value Disclosure	$ 92	$ 101
Asset-backed Securities [Member] | Weighted Average [Member] | Valuation, Market Approach [Member]
Fair Value, Option, Quantitative Disclosures [Line Items]
Debt Instrument, Measurement Input	0.03	0.01
Asset-backed Securities [Member] | Maximum [Member] | Valuation, Market Approach [Member]
Fair Value, Option, Quantitative Disclosures [Line Items]
Debt Instrument, Measurement Input	0.18	0.04
Asset-backed Securities [Member] | Minimum [Member] | Valuation, Market Approach [Member]
Fair Value, Option, Quantitative Disclosures [Line Items]
Debt Instrument, Measurement Input	0.00	0.00
Corporate Debt Securities [Member] | Valuation, Market Approach [Member]
Fair Value, Option, Quantitative Disclosures [Line Items]
Assets, Fair Value Disclosure	$ 1,030	$ 1,070
Corporate Debt Securities [Member] | Weighted Average [Member] | Valuation, Market Approach [Member]
Fair Value, Option, Quantitative Disclosures [Line Items]
Debt Instrument, Measurement Input	0.01	0.01
Corporate Debt Securities [Member] | Maximum [Member] | Valuation, Market Approach [Member]
Fair Value, Option, Quantitative Disclosures [Line Items]
Debt Instrument, Measurement Input	0.02	0.02
Corporate Debt Securities [Member] | Minimum [Member] | Valuation, Market Approach [Member]
Fair Value, Option, Quantitative Disclosures [Line Items]
Debt Instrument, Measurement Input	0.00	0.00
Funds Withheld At Interest Embedded Derivatives [Member]
Fair Value, Option, Quantitative Disclosures [Line Items]
Assets, Fair Value Disclosure	$ (109)	$ 121
US Government Agencies Debt Securities [Member]
Fair Value, Option, Quantitative Disclosures [Line Items]
Assets, Fair Value Disclosure	$ 15	$ 16
US Government Agencies Debt Securities [Member] | Weighted Average [Member] | Valuation, Market Approach [Member]
Fair Value, Option, Quantitative Disclosures [Line Items]
Debt Instrument, Measurement Input	0.01	0.01
US Government Agencies Debt Securities [Member] | Maximum [Member] | Valuation, Market Approach [Member]
Fair Value, Option, Quantitative Disclosures [Line Items]
Debt Instrument, Measurement Input	0.01	0.01
US Government Agencies Debt Securities [Member] | Minimum [Member] | Valuation, Market Approach [Member]
Fair Value, Option, Quantitative Disclosures [Line Items]
Debt Instrument, Measurement Input	0.00	0.00
Foreign Government Debt [Member]
Fair Value, Option, Quantitative Disclosures [Line Items]
Assets, Fair Value Disclosure	$ 15	$ 16
Equity Securities [Member] | Valuation, Market Approach [Member]
Fair Value, Option, Quantitative Disclosures [Line Items]
Assets, Fair Value Disclosure	$ 29	$ 32
Equity Securities [Member] | Weighted Average [Member] | Valuation, Market Approach [Member]
Fair Value, Option, Quantitative Disclosures [Line Items]
Equity Securities, FV-NI, Measurement Input	0.04	0.04
Equity Securities [Member] | Maximum [Member] | Valuation, Market Approach [Member]
Fair Value, Option, Quantitative Disclosures [Line Items]
Equity Securities, FV-NI, Measurement Input	0.04	0.04
Equity Securities [Member] | Minimum [Member] | Valuation, Market Approach [Member]
Fair Value, Option, Quantitative Disclosures [Line Items]
Equity Securities, FV-NI, Measurement Input	0.04	0.04
Embedded Derivatives In Indexed Annuity [Member] | Valuation, Income Approach [Member]
Fair Value, Option, Quantitative Disclosures [Line Items]
Financial and Nonfinancial Liabilities, Fair Value Disclosure	$ 751	$ 768
Embedded Derivatives In Indexed Annuity [Member] | Weighted Average [Member] | Valuation Technique, Discounted Cash Flow [Member]
Fair Value, Option, Quantitative Disclosures [Line Items]
Embedded Derivative Liability, Measurement Input	0.02	0.02
Embedded Derivatives In Indexed Annuity [Member] | Maximum [Member] | Valuation Technique, Discounted Cash Flow [Member]
Fair Value, Option, Quantitative Disclosures [Line Items]
Embedded Derivative Liability, Measurement Input	0.04	0.04
Embedded Derivatives In Indexed Annuity [Member] | Minimum [Member] | Valuation Technique, Discounted Cash Flow [Member]
Fair Value, Option, Quantitative Disclosures [Line Items]
Embedded Derivative Liability, Measurement Input	0.02	0.02
Embedded Derivatives In Variable Annuity [Member] | Valuation, Income Approach [Member]
Fair Value, Option, Quantitative Disclosures [Line Items]
Financial and Nonfinancial Liabilities, Fair Value Disclosure	$ 291	$ 163
Debt Security, Corporate, Non-US [Member] | Weighted Average [Member] | Valuation, Market Approach [Member]
Fair Value, Option, Quantitative Disclosures [Line Items]
Debt Instrument, Measurement Input	0.01	0.01
Debt Security, Corporate, Non-US [Member] | Maximum [Member] | Valuation, Market Approach [Member]
Fair Value, Option, Quantitative Disclosures [Line Items]
Debt Instrument, Measurement Input	0.01	0.01
Debt Security, Corporate, Non-US [Member] | Minimum [Member] | Valuation, Market Approach [Member]
Fair Value, Option, Quantitative Disclosures [Line Items]
Debt Instrument, Measurement Input	0.00	0.00
Measurement Input, Long-term Revenue Growth Rate [Member] | Embedded Derivatives In Variable Annuity [Member] | Weighted Average [Member] | Valuation Technique, Discounted Cash Flow [Member]
Fair Value, Option, Quantitative Disclosures [Line Items]
Embedded Derivative Liability, Measurement Input	0.12	0.12
Measurement Input, Long-term Revenue Growth Rate [Member] | Embedded Derivatives In Variable Annuity [Member] | Maximum [Member] | Valuation Technique, Discounted Cash Flow [Member]
Fair Value, Option, Quantitative Disclosures [Line Items]
Embedded Derivative Liability, Measurement Input	0.27	0.27
Measurement Input, Long-term Revenue Growth Rate [Member] | Embedded Derivatives In Variable Annuity [Member] | Minimum [Member] | Valuation Technique, Discounted Cash Flow [Member]
Fair Value, Option, Quantitative Disclosures [Line Items]
Embedded Derivative Liability, Measurement Input	0.00	0.00
Measurement Input Mortality Improvement [Member] | Longevity Swap [Member] | Weighted Average [Member] | Valuation Technique, Discounted Cash Flow [Member]
Fair Value, Option, Quantitative Disclosures [Line Items]
Debt Instrument, Measurement Input	0.00	0.00
Measurement Input Mortality Improvement [Member] | Longevity Swap [Member] | Maximum [Member] | Valuation Technique, Discounted Cash Flow [Member]
Fair Value, Option, Quantitative Disclosures [Line Items]
Debt Instrument, Measurement Input	0.00	0.00
Measurement Input Mortality Improvement [Member] | Longevity Swap [Member] | Minimum [Member] | Valuation Technique, Discounted Cash Flow [Member]
Fair Value, Option, Quantitative Disclosures [Line Items]
Debt Instrument, Measurement Input	0.00	0.00
Measurement Input Crediting Rate [Member] | Funds Withheld At Interest Embedded Derivatives [Member] | Weighted Average [Member] | Valuation, Income Approach [Member]
Fair Value, Option, Quantitative Disclosures [Line Items]
Embedded Derivative Asset, Measurement Input	0.02	0.02
Measurement Input Crediting Rate [Member] | Funds Withheld At Interest Embedded Derivatives [Member] | Maximum [Member] | Valuation, Income Approach [Member]
Fair Value, Option, Quantitative Disclosures [Line Items]
Embedded Derivative Asset, Measurement Input	0.04	0.04
Measurement Input Crediting Rate [Member] | Funds Withheld At Interest Embedded Derivatives [Member] | Minimum [Member] | Valuation, Income Approach [Member]
Fair Value, Option, Quantitative Disclosures [Line Items]
Embedded Derivative Asset, Measurement Input	0.02	0.02
Measurement Input, Counterparty Credit Risk [Member] | Funds Withheld At Interest Embedded Derivatives [Member] | Weighted Average [Member] | Valuation, Income Approach [Member]
Fair Value, Option, Quantitative Disclosures [Line Items]
Embedded Derivative Asset, Measurement Input	0.01	0.01
Measurement Input, Counterparty Credit Risk [Member] | Funds Withheld At Interest Embedded Derivatives [Member] | Maximum [Member] | Valuation, Income Approach [Member]
Fair Value, Option, Quantitative Disclosures [Line Items]
Embedded Derivative Asset, Measurement Input	0.05	0.05
Measurement Input, Counterparty Credit Risk [Member] | Funds Withheld At Interest Embedded Derivatives [Member] | Minimum [Member] | Valuation, Income Approach [Member]
Fair Value, Option, Quantitative Disclosures [Line Items]
Embedded Derivative Asset, Measurement Input	0.00	0.00
Measurement Input, Counterparty Credit Risk [Member] | Embedded Derivatives In Variable Annuity [Member] | Weighted Average [Member] | Valuation Technique, Discounted Cash Flow [Member]
Fair Value, Option, Quantitative Disclosures [Line Items]
Embedded Derivative Liability, Measurement Input	0.01	0.01
Measurement Input, Counterparty Credit Risk [Member] | Embedded Derivatives In Variable Annuity [Member] | Maximum [Member] | Valuation Technique, Discounted Cash Flow [Member]
Fair Value, Option, Quantitative Disclosures [Line Items]
Embedded Derivative Liability, Measurement Input	0.05	0.05
Measurement Input, Counterparty Credit Risk [Member] | Embedded Derivatives In Variable Annuity [Member] | Minimum [Member] | Valuation Technique, Discounted Cash Flow [Member]
Fair Value, Option, Quantitative Disclosures [Line Items]
Embedded Derivative Liability, Measurement Input	0.00	0.00
Measurement Input, Withdrawal Rate [Member] | Funds Withheld At Interest Embedded Derivatives [Member] | Weighted Average [Member] | Valuation, Income Approach [Member]
Fair Value, Option, Quantitative Disclosures [Line Items]
Embedded Derivative Asset, Measurement Input	0.03	0.03
Measurement Input, Withdrawal Rate [Member] | Funds Withheld At Interest Embedded Derivatives [Member] | Maximum [Member] | Valuation, Income Approach [Member]
Fair Value, Option, Quantitative Disclosures [Line Items]
Embedded Derivative Asset, Measurement Input	0.05	0.05
Measurement Input, Withdrawal Rate [Member] | Funds Withheld At Interest Embedded Derivatives [Member] | Minimum [Member] | Valuation, Income Approach [Member]
Fair Value, Option, Quantitative Disclosures [Line Items]
Embedded Derivative Asset, Measurement Input	0.00	0.00
Measurement Input, Withdrawal Rate [Member] | Embedded Derivatives In Indexed Annuity [Member] | Weighted Average [Member] | Valuation Technique, Discounted Cash Flow [Member]
Fair Value, Option, Quantitative Disclosures [Line Items]
Embedded Derivative Liability, Measurement Input	0.03	0.03
Measurement Input, Withdrawal Rate [Member] | Embedded Derivatives In Indexed Annuity [Member] | Maximum [Member] | Valuation Technique, Discounted Cash Flow [Member]
Fair Value, Option, Quantitative Disclosures [Line Items]
Embedded Derivative Liability, Measurement Input	0.05	0.05
Measurement Input, Withdrawal Rate [Member] | Embedded Derivatives In Indexed Annuity [Member] | Minimum [Member] | Valuation Technique, Discounted Cash Flow [Member]
Fair Value, Option, Quantitative Disclosures [Line Items]
Embedded Derivative Liability, Measurement Input	0.00	0.00
Measurement Input, Withdrawal Rate [Member] | Embedded Derivatives In Variable Annuity [Member] | Weighted Average [Member] | Valuation Technique, Discounted Cash Flow [Member]
Fair Value, Option, Quantitative Disclosures [Line Items]
Embedded Derivative Liability, Measurement Input	0.06	0.05
Measurement Input, Withdrawal Rate [Member] | Embedded Derivatives In Variable Annuity [Member] | Maximum [Member] | Valuation Technique, Discounted Cash Flow [Member]
Fair Value, Option, Quantitative Disclosures [Line Items]
Embedded Derivative Liability, Measurement Input	0.07	0.07
Measurement Input, Withdrawal Rate [Member] | Embedded Derivatives In Variable Annuity [Member] | Minimum [Member] | Valuation Technique, Discounted Cash Flow [Member]
Fair Value, Option, Quantitative Disclosures [Line Items]
Embedded Derivative Liability, Measurement Input	0.00	0.00
Measurement Input, Lapse Rate [Member] | Funds Withheld At Interest Embedded Derivatives [Member] | Weighted Average [Member] | Valuation, Income Approach [Member]
Fair Value, Option, Quantitative Disclosures [Line Items]
Embedded Derivative Asset, Measurement Input	0.14	0.13
Measurement Input, Lapse Rate [Member] | Funds Withheld At Interest Embedded Derivatives [Member] | Maximum [Member] | Valuation, Income Approach [Member]
Fair Value, Option, Quantitative Disclosures [Line Items]
Embedded Derivative Asset, Measurement Input	0.35	0.35
Measurement Input, Lapse Rate [Member] | Funds Withheld At Interest Embedded Derivatives [Member] | Minimum [Member] | Valuation, Income Approach [Member]
Fair Value, Option, Quantitative Disclosures [Line Items]
Embedded Derivative Asset, Measurement Input	0.00	0.00
Measurement Input, Lapse Rate [Member] | Embedded Derivatives In Indexed Annuity [Member] | Weighted Average [Member] | Valuation Technique, Discounted Cash Flow [Member]
Fair Value, Option, Quantitative Disclosures [Line Items]
Embedded Derivative Liability, Measurement Input	0.14	0.13
Measurement Input, Lapse Rate [Member] | Embedded Derivatives In Indexed Annuity [Member] | Maximum [Member] | Valuation Technique, Discounted Cash Flow [Member]
Fair Value, Option, Quantitative Disclosures [Line Items]
Embedded Derivative Liability, Measurement Input	0.35	0.35
Measurement Input, Lapse Rate [Member] | Embedded Derivatives In Indexed Annuity [Member] | Minimum [Member] | Valuation Technique, Discounted Cash Flow [Member]
Fair Value, Option, Quantitative Disclosures [Line Items]
Embedded Derivative Liability, Measurement Input	0.00	0.00
Measurement Input, Lapse Rate [Member] | Embedded Derivatives In Variable Annuity [Member] | Weighted Average [Member] | Valuation Technique, Discounted Cash Flow [Member]
Fair Value, Option, Quantitative Disclosures [Line Items]
Embedded Derivative Liability, Measurement Input	0.04	0.05
Measurement Input, Lapse Rate [Member] | Embedded Derivatives In Variable Annuity [Member] | Maximum [Member] | Valuation Technique, Discounted Cash Flow [Member]
Fair Value, Option, Quantitative Disclosures [Line Items]
Embedded Derivative Liability, Measurement Input	0.25	0.25
Measurement Input, Lapse Rate [Member] | Embedded Derivatives In Variable Annuity [Member] | Minimum [Member] | Valuation Technique, Discounted Cash Flow [Member]
Fair Value, Option, Quantitative Disclosures [Line Items]
Embedded Derivative Liability, Measurement Input	0.00	0.00
Measurement Input, Mortality Rate [Member] | Longevity Swap [Member] | Weighted Average [Member] | Valuation Technique, Discounted Cash Flow [Member]
Fair Value, Option, Quantitative Disclosures [Line Items]
Debt Instrument, Measurement Input	0.00	0.00
Measurement Input, Mortality Rate [Member] | Longevity Swap [Member] | Maximum [Member] | Valuation Technique, Discounted Cash Flow [Member]
Fair Value, Option, Quantitative Disclosures [Line Items]
Debt Instrument, Measurement Input	0.00	0.00
Measurement Input, Mortality Rate [Member] | Longevity Swap [Member] | Minimum [Member] | Valuation Technique, Discounted Cash Flow [Member]
Fair Value, Option, Quantitative Disclosures [Line Items]
Debt Instrument, Measurement Input	0.00	0.00
Measurement Input, Mortality Rate [Member] | Funds Withheld At Interest Embedded Derivatives [Member] | Weighted Average [Member] | Valuation, Income Approach [Member]
Fair Value, Option, Quantitative Disclosures [Line Items]
Embedded Derivative Asset, Measurement Input	0.02	0.02
Measurement Input, Mortality Rate [Member] | Funds Withheld At Interest Embedded Derivatives [Member] | Maximum [Member] | Valuation, Income Approach [Member]
Fair Value, Option, Quantitative Disclosures [Line Items]
Embedded Derivative Asset, Measurement Input	1.00	1.00
Measurement Input, Mortality Rate [Member] | Funds Withheld At Interest Embedded Derivatives [Member] | Minimum [Member] | Valuation, Income Approach [Member]
Fair Value, Option, Quantitative Disclosures [Line Items]
Embedded Derivative Asset, Measurement Input	0.00	0.00
Measurement Input, Mortality Rate [Member] | Embedded Derivatives In Indexed Annuity [Member] | Weighted Average [Member] | Valuation Technique, Discounted Cash Flow [Member]
Fair Value, Option, Quantitative Disclosures [Line Items]
Embedded Derivative Liability, Measurement Input	0.02	0.02
Measurement Input, Mortality Rate [Member] | Embedded Derivatives In Indexed Annuity [Member] | Maximum [Member] | Valuation Technique, Discounted Cash Flow [Member]
Fair Value, Option, Quantitative Disclosures [Line Items]
Embedded Derivative Liability, Measurement Input	1.00	1.00
Measurement Input, Mortality Rate [Member] | Embedded Derivatives In Indexed Annuity [Member] | Minimum [Member] | Valuation Technique, Discounted Cash Flow [Member]
Fair Value, Option, Quantitative Disclosures [Line Items]
Embedded Derivative Liability, Measurement Input	0.00	0.00
Measurement Input, Mortality Rate [Member] | Embedded Derivatives In Variable Annuity [Member] | Weighted Average [Member] | Valuation Technique, Discounted Cash Flow [Member]
Fair Value, Option, Quantitative Disclosures [Line Items]
Embedded Derivative Liability, Measurement Input	0.02	0.01
Measurement Input, Mortality Rate [Member] | Embedded Derivatives In Variable Annuity [Member] | Maximum [Member] | Valuation Technique, Discounted Cash Flow [Member]
Fair Value, Option, Quantitative Disclosures [Line Items]
Embedded Derivative Liability, Measurement Input	1.00	1.00
Measurement Input, Mortality Rate [Member] | Embedded Derivatives In Variable Annuity [Member] | Minimum [Member] | Valuation Technique, Discounted Cash Flow [Member]
Fair Value, Option, Quantitative Disclosures [Line Items]
Embedded Derivative Liability, Measurement Input	0.00	0.00
Measurement Input, Mortality Rate [Member] | Mortality Swap [Member] | Weighted Average [Member] | Valuation Technique, Discounted Cash Flow [Member]
Fair Value, Option, Quantitative Disclosures [Line Items]
Debt Instrument, Measurement Input	0.00	0.00
Measurement Input, Mortality Rate [Member] | Mortality Swap [Member] | Maximum [Member] | Valuation Technique, Discounted Cash Flow [Member]
Fair Value, Option, Quantitative Disclosures [Line Items]
Debt Instrument, Measurement Input	0.00	0.00
Measurement Input, Mortality Rate [Member] | Mortality Swap [Member] | Minimum [Member] | Valuation Technique, Discounted Cash Flow [Member]
Fair Value, Option, Quantitative Disclosures [Line Items]
Debt Instrument, Measurement Input	0.00	0.00
Measurement Input, EBITDA Multiple [Member] | Corporate Debt Securities [Member] | Weighted Average [Member] | Valuation, Market Approach [Member]
Fair Value, Option, Quantitative Disclosures [Line Items]
Debt Instrument, Measurement Input	6.3	6.7
Measurement Input, EBITDA Multiple [Member] | Corporate Debt Securities [Member] | Maximum [Member] | Valuation, Market Approach [Member]
Fair Value, Option, Quantitative Disclosures [Line Items]
Debt Instrument, Measurement Input	7.0	7.1
Measurement Input, EBITDA Multiple [Member] | Corporate Debt Securities [Member] | Minimum [Member] | Valuation, Market Approach [Member]
Fair Value, Option, Quantitative Disclosures [Line Items]
Debt Instrument, Measurement Input	5.2	5.2
Measurement Input, EBITDA Multiple [Member] | Equity Securities [Member] | Weighted Average [Member] | Valuation, Market Approach [Member]
Fair Value, Option, Quantitative Disclosures [Line Items]
Equity Securities, FV-NI, Measurement Input	8.0	7.8
Measurement Input, EBITDA Multiple [Member] | Equity Securities [Member] | Maximum [Member] | Valuation, Market Approach [Member]
Fair Value, Option, Quantitative Disclosures [Line Items]
Equity Securities, FV-NI, Measurement Input	10.6	9.3
Measurement Input, EBITDA Multiple [Member] | Equity Securities [Member] | Minimum [Member] | Valuation, Market Approach [Member]
Fair Value, Option, Quantitative Disclosures [Line Items]
Equity Securities, FV-NI, Measurement Input	6.9	6.9