Investments - Net Investment Income (Details) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Gross investment income	$ 141,000,000	$ 231,000,000	$ 347,000,000	$ 430,000,000
Investment expenses	(9,000,000)	(9,000,000)	(17,000,000)	(18,000,000)
Net investment income (excluding net realized capital gains or losses)	132,000,000	222,000,000	330,000,000	412,000,000
Net realized capital gains	52,000,000	71,000,000	16,000,000	130,000,000
Net investment income	184,000,000	293,000,000	346,000,000	542,000,000
Credit-related impairment loss (reversal of loss)	(42,000,000)		3,000,000
Yield-related impairment loss	1,000,000		42,000,000
Other-than-temporary impairment loss		6,000,000		13,000,000
Supporting experience-rated products
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Net investment income	10,000,000	12,000,000	21,000,000	23,000,000
Debt securities
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Gross investment income	146,000,000	146,000,000	290,000,000	292,000,000
Mortgage loans
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Gross investment income	15,000,000	18,000,000	30,000,000	35,000,000
Other investments
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Gross investment income	$ (20,000,000)	$ 67,000,000	$ 27,000,000	$ 103,000,000