Investments - Net Investment Income (Details) - USD ($) $ in Millions	3 Months Ended
Mar. 31, 2021	Mar. 31, 2020
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Gross investment income	$ 258	$ 206
Investment expenses	(8)	(8)
Net investment income (excluding net realized capital gains or losses)	250	198
Net realized capital gains	47	(36)
Net investment income	297	162
Yield-related impairment loss	(30)	(45)
Credit-related impairment loss	0	(41)
Supporting experience-rated products
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Net investment income	9	11
Debt securities
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Gross investment income	157	144
Mortgage loans
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Gross investment income	15	15
Other investments
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Gross investment income	$ 86	$ 47

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