Investments - Net investment income (Details) - USD ($) $ in Millions	3 Months Ended
Mar. 31, 2020	Mar. 31, 2019
Net Investment Income:
Investment income, before expense	$ 479	$ 719
Investment expense	(58)	(71)
Net investment income	421	648
Fixed income securities
Net Investment Income:
Investment income, before expense	525	538
Equity securities
Net Investment Income:
Investment income, before expense	6	30
Mortgage loans
Net Investment Income:
Investment income, before expense	60	53
Limited partnership interests
Net Investment Income:
Limited partnership interests	(192)	9
Net investment income	(52)
Net Investment Income, Excluded from Value Increase	(195)
Short-term investments
Net Investment Income:
Investment income, before expense	17	26
Other
Net Investment Income:
Investment income, before expense	$ 63	$ 63

Interest and Dividend Income (Expenses), Operating

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Net Investment Income, Excluded from Value Increase

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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.

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Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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