Commitments and Contingent Liabilities (Narrative) (Details) - USD ($) $ in Millions	Sep. 30, 2018	Dec. 31, 2017
Commitments and Contingent Liabilities [Line Items]
Litigation and regulatory matters loss contingency, range of possible loss, maximum (less than)	$ 150
Commitments \| Commercial Mortgage Loans
Commitments and Contingent Liabilities [Line Items]
Total outstanding mortgage loan commitments	2	$ 37
Commitments \| Investments
Commitments and Contingent Liabilities [Line Items]
Commitments to Purchase Investment (excluding Commercial Mortgage Loans)	$ 138	$ 134

The difference between the maximum amount of estimated loss and the amount recorded as of the balance sheet date.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 450
-SubTopic 20
-Section 05
-Paragraph 5
-URI http://asc.fasb.org/extlink&oid=99385795&loc=d3e12631-108344

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- Definition

Amount of investment in mortgage loan on real estate by entity with substantial portion of business acquiring and holding investment real estate or interest in real estate.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 948
-SubTopic 310
-Section S99
-Paragraph 1
-Subparagraph (SX 210.12-29(Column G))
-URI http://asc.fasb.org/extlink&oid=6589523&loc=d3e617274-123014

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- Definition

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.

+ References

No definition available.

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- Definition

Minimum amount of purchase arrangement in which the entity has agreed to expend funds to procure goods or services from a supplier.

+ References

No definition available.

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- Details

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