Investments - Investment Income (Details) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Gross investment income	$ 224,000,000	$ 221,000,000	$ 654,000,000	$ 485,000,000
Investment expenses	(10,000,000)	0	(28,000,000)	0
Net investment income (excluding net realized capital gains or losses)	214,000,000	221,000,000	626,000,000	485,000,000
Net realized capital gains	49,000,000	0	179,000,000	0
Net investment income	263,000,000	221,000,000	805,000,000	485,000,000
OTTI losses, investments, portion recognized in earnings, net	(9,000,000)	0	(22,000,000)	0
Supporting experience-rated products
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Net investment income	10,000,000	0	33,000,000	0
Debt securities
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Gross investment income	145,000,000	2,000,000	437,000,000	5,000,000
Mortgage loans
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Gross investment income	19,000,000	0	54,000,000	0
Other investments
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Gross investment income	$ 60,000,000	$ 219,000,000	$ 163,000,000	$ 480,000,000