Investments - Net Investment Income (Details) - USD ($)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Gross investment income	$ 781,000,000	$ 854,000,000	$ 660,000,000
Investment expenses	(35,000,000)	(42,000,000)	(3,000,000)
Net investment income (excluding net realized capital gains or losses)	746,000,000	812,000,000	657,000,000
Net realized capital gains	52,000,000	199,000,000	3,000,000
Net investment income	798,000,000	1,011,000,000	660,000,000
Credit-related impairment loss (reversal of loss)	0
Yield-related impairment loss	(49,000,000)
OTTI losses, investments, portion recognized in earnings, net		(24,000,000)	0
Supporting experience- rated products
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Net investment income	42,000,000	44,000,000	4,000,000
Debt securities
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Gross investment income	598,000,000	589,000,000	61,000,000
Mortgage loans
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Gross investment income	60,000,000	71,000,000	6,000,000
Other investments
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Gross investment income	$ 123,000,000	$ 194,000,000	$ 593,000,000