Financial Instruments Narrative (Details) bbl in Millions, $ in Millions	3 Months Ended	12 Months Ended
Mar. 31, 2018 USD ($) bbl	Dec. 31, 2017 USD ($) bbl
Derivative [Line Items]
Debt designated as net investment in foreign operations \| $	$ 901	$ 884
Investment Segment
Derivative [Line Items]
Fair value derivative instruments with credit risk related contingent features in a liability position \| $	$ 0	$ 17
Not designated as hedging instrument \| Commodity contracts \| Energy Segment
Derivative [Line Items]
Volume of derivatives (barrels) \| bbl	2.9	14.3
Not designated as hedging instrument \| Commodity contracts not considered probable of settlement [Member] \| Energy Segment
Derivative [Line Items]
Volume of derivatives (barrels) \| bbl	4.2	5.8

Fair value of credit risk derivative liability.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 825
-SubTopic 10
-Section 50
-Paragraph 10
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=77997519&loc=d3e13433-108611

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 4K
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=84234895&loc=SL5708775-113959

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Nominal volume used to calculate payments on a derivative instrument.

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- Definition

Fair value of all derivative liabilities designated as hedges of net investment in foreign operations.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 4B
-Subparagraph (c)(1)
-URI http://asc.fasb.org/extlink&oid=84234895&loc=SL5624163-113959

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