Investments - Net Investment Income (Details) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Gross investment income	$ 203,000,000	$ 224,000,000	$ 550,000,000	$ 654,000,000
Investment expenses	(8,000,000)	(10,000,000)	(25,000,000)	(28,000,000)
Net investment income (excluding net realized capital gains or losses)	195,000,000	214,000,000	525,000,000	626,000,000
Net realized capital gains	9,000,000	49,000,000	25,000,000	179,000,000
Net investment income	204,000,000	263,000,000	550,000,000	805,000,000
Credit-related impairment loss (reversal of loss)	1,000,000		4,000,000
Yield-related impairment loss	2,000,000		44,000,000
Other-than-temporary impairment loss		9,000,000		22,000,000
Supporting experience-rated products
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Net investment income	10,000,000	10,000,000	31,000,000	33,000,000
Debt securities
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Gross investment income	151,000,000	145,000,000	441,000,000	437,000,000
Mortgage loans
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Gross investment income	15,000,000	19,000,000	45,000,000	54,000,000
Other investments
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Gross investment income	$ 37,000,000	$ 60,000,000	$ 64,000,000	$ 163,000,000