Investments and Cash - Net Investment Income (Details) - USD ($) $ in Millions	3 Months Ended	6 Months Ended
Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Net Investment Income
Gross investment income	$ 102	$ 103	$ 205	$ 227
Investment expenses	(3)	(2)	(5)	(4)
Net investment income	99	101	200	223
Fixed Maturities, Managed Externally [Member]
Net Investment Income
Gross investment income	74	75	149	150
Fixed Maturities, Managed Internally [Member]
Net Investment Income
Gross investment income	$ 28	$ 28	$ 56	$ 77

Represents the total of interest and dividend income, including any amortization and accretion (as applicable) of discounts and premiums, earned from (1) loans and leases whether held-for-sale or held-in-portfolio; (2) investment securities; (3) federal funds sold; (4) securities purchased under agreements to resell; (5) investments in banker's acceptances, commercial paper, or certificates of deposit; (6) dividend income; or (7) other investments not otherwise specified herein.

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Amount of expenses related to the generation of investment income.

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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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