Investments - Net investment income (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Net investment income
Investment income, before expense	$ 1,323	$ 1,515	$ 1,688
Investment expense	(81)	(104)	(103)
Net investment income	1,242	1,411	1,585
Fixed income securities
Net investment income
Investment income, before expense	894	963	991
Mortgage loans
Net investment income
Investment income, before expense	184	190	188
Equity securities
Net investment income
Investment income, before expense	19	29	39
Limited partnership interests
Net investment income
Investment income, before expense	99	175	327
Short-term investments
Net investment income
Investment income, before expense	6	31	21
Policy loans
Net investment income
Investment income, before expense	31	34	31
Other
Net investment income
Investment income, before expense	$ 90	$ 93	$ 91

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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