Financial Instruments - Hedges (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Designated as hedging instrument \| Cash flow hedging
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Effect on hedging instrument	$ (6)	$ 8	$ 38
Effect on underlying	6	(8)	(38)
Effect on earnings	0	0	0
Not designated as hedging instrument, economic hedge
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Effect on hedging instrument	(4)	121	(272)
Effect on underlying	(34)	(152)	102
Effect on earnings	$ (38)	$ (31)	$ (170)

Amount of the increase (decrease) in fair value of the hedged item in a fair value hedge recognized in the income statement.

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- Definition

Amount of increase (decrease) in the fair value of derivatives recognized in the income statement.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 4A
-Subparagraph (b)(1)
-URI http://asc.fasb.org/extlink&oid=109980867&loc=SL5618551-113959

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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.

+ References

No definition available.

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- Definition

Amount of gain (loss) from the ineffectiveness of the hedge.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 25
-Section 50
-Paragraph 1
-Subparagraph (a)(1)
-URI http://asc.fasb.org/extlink&oid=109977999&loc=d3e76258-113986

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 4C
-Subparagraph (d)(1)
-URI http://asc.fasb.org/extlink&oid=109980867&loc=SL5624171-113959

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