Investments - Investment Income (Details) - USD ($)	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Gross investment income	$ 206,000,000	$ 199,000,000
Investment expenses	(8,000,000)	(9,000,000)
Net investment income (excluding net realized capital gains or losses)	198,000,000	190,000,000
Net realized capital gains (losses)	(36,000,000)	59,000,000
Net investment income	162,000,000	249,000,000
Credit-related impairment loss	45,000,000
Yield-related impairment loss	41,000,000
Other-than-temporary impairment loss		7,000,000
Supporting experience-rated products
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Net investment income	11,000,000	11,000,000
Debt securities
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Gross investment income	144,000,000	156,000,000
Mortgage loans
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Gross investment income	15,000,000	17,000,000
Other investments
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Gross investment income	$ 47,000,000	$ 26,000,000