Investments - Net investment income (Details) - USD ($) $ in Millions	3 Months Ended
Mar. 31, 2021	Mar. 31, 2020
Net Investment Income:
Investment income, before expense	$ 745	$ 282
Investment expense	(37)	(36)
Net investment income	708	246
Fixed income securities
Net Investment Income:
Investment income, before expense	301	298
Equity securities
Net Investment Income:
Investment income, before expense	14	10
Mortgage loans
Net Investment Income:
Investment income, before expense	10	9
Limited partnership interests
Net Investment Income:
Investment income, before expense	378	(77)
Short-term investments
Net Investment Income:
Investment income, before expense	1	11
Other
Net Investment Income:
Investment income, before expense	$ 41	$ 31

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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