Aggregate notional amount specified by the derivative(s). Expressed as an absolute value.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Article 12
-Section 13
-Sentence Column B

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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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- 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

Period the derivative contract is outstanding, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

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Derivatives and Risk Management - Narrative (Details) € in Millions, ¥ in Millions, $ in Millions, $ in Millions	1 Months Ended		3 Months Ended		6 Months Ended
	Apr. 30, 2018 USD ($)	Jan. 31, 2018 EUR (€)	Jun. 30, 2018 USD ($)	Jun. 30, 2017 USD ($)	Jun. 30, 2018 USD ($)	Jun. 30, 2017 USD ($)	Jun. 30, 2018 EUR (€)	Jun. 30, 2018 JPY (¥)	Jun. 30, 2018 USD ($)	Dec. 31, 2017 JPY (¥)	Dec. 31, 2017 CAD ($)
Fuel hedge contracts
Derivative
Derivative gains (losses)			$ (94)	$ 40	$ (92)	$ 97
Foreign currency exchange contracts
Derivative
Derivative gains (losses)			$ 22		$ 6
Foreign currency exchange contracts \| Not designated as hedging instrument
Derivative
Derivative, notional amount \| €							€ 375
Cash flow hedge \| Foreign currency exchange contracts \| Not designated as hedging instrument
Derivative
Derivative, term of contract		3 years
Derivative, notional amount \| €		€ 375
Cash flow hedge \| Foreign currency exchange contracts \| Designated as hedging instrument
Derivative
Derivative, notional amount								¥ 15,285		¥ 23,512	$ 490
Fair value hedge \| Interest rate contracts \| Designated as hedging instrument
Derivative
Derivative, notional amount	$ 1,600								$ 1,908
Minimum \| Fair value hedge \| Interest rate contracts \| Designated as hedging instrument
Derivative
Derivative, term of contract	3 years
Maximum \| Fair value hedge \| Interest rate contracts \| Designated as hedging instrument
Derivative
Derivative, term of contract	10 years