Investments - Investment Income (Details) $ in Millions	12 Months Ended
Dec. 31, 2018 USD ($)
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Gross investment income	$ 660
Investment expenses	(3)
Net investment income (excluding net realized capital gains or losses)	657
Net realized capital gains	3
Net Investment Income	660
Debt securities
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Gross investment income	61
Mortgage loans
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Gross investment income	6
Other investments
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Gross investment income	593
Supporting experience-rated products
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Net Investment Income	$ 4

Investment Income, Excluding Capital Gains

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

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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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