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	637
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	17
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 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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Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 225
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03.8)
-URI http://asc.fasb.org/extlink&oid=63488584&loc=d3e20235-122688

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-Topic 225
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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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Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 225
-Section S99
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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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