Investments - Investment Income (Details) - USD ($)	3 Months Ended	6 Months Ended
Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Gross investment income	$ 231,000,000	$ 214,000,000	$ 430,000,000	$ 264,000,000
Investment expenses	(9,000,000)	0	(18,000,000)	0
Net investment income (excluding net realized capital gains or losses)	222,000,000	214,000,000	412,000,000	264,000,000
Net realized capital gains	71,000,000	0	130,000,000	0
Net investment income	293,000,000	214,000,000	542,000,000	264,000,000
OTTI losses, investments, portion recognized in earnings, net	6,000,000	0	13,000,000	0
Supporting experience-rated products
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Net investment income	12,000,000	0	23,000,000	0
Debt securities
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Gross investment income	146,000,000	1,000,000	292,000,000	3,000,000
Mortgage loans
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Gross investment income	18,000,000	0	35,000,000	0
Other investments
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Gross investment income	$ 67,000,000	$ 213,000,000	$ 103,000,000	$ 261,000,000

Investment Income, Excluding Capital Gains or Losses

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Amount before accretion (amortization) of purchase discount (premium) of interest income and dividend income on nonoperating securities.

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Amount of expenses related to the generation of investment income.

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Amount after accretion (amortization) of discount (premium), and investment expense, of interest income and dividend income on nonoperating securities.

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Amount of other-than-temporary impairment (OTTI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), recognized in earnings.

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The net realized gains or losses on investments during the period, not including gains or losses on securities separately or otherwise categorized as trading, available-for-sale, or held-to-maturity.

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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