Investments - Net Investment Income (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Net Investment Income [Line Items]
Investment expenses	$ (83)	$ (77)	$ (71)
Total net investment income	1,951	1,780	1,603
Total fixed maturities
Net Investment Income [Line Items]
Gross investment income	1,559	1,459	1,303
Equity securities
Net Investment Income [Line Items]
Gross investment income	46	32	24
Mortgage loans
Net Investment Income [Line Items]
Gross investment income	165	141	124
Limited partnerships and other alternative investments
Net Investment Income [Line Items]
Gross investment income	232	205	174
Other investments
Net Investment Income [Line Items]
Gross investment income	$ 32	$ 20	$ 49

Amount, before investment expense, of income earned from investments in securities and real estate. Includes, but is not limited to, real estate investment, policy loans, dividends, and interest. Excludes realized gain (loss) on investments.

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Amount, after investment expense, of income earned from investments in securities and real estate. Includes, but is not limited to, real estate investment, policy loans, dividends, and interest. Excludes realized gain (loss) on investments.

+ References

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