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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Amount of obligation to return cash collateral under master netting arrangements that have not been offset against derivative assets.

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Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 20
-Section 55
-Paragraph 13
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-Paragraph 3
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Amount of right to receive cash collateral under master netting arrangements that have not been offset against derivative liabilities.

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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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- Definition

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

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 4A
-Subparagraph (b)(1)
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Period the derivative contract is outstanding, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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The difference between the book value and the sale price of options, swaps, futures, forward contracts, and other derivative instruments. This element refers to the gain (loss) included in earnings.

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Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 28
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-Topic 942
-SubTopic 220
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-04.13(h))
-URI http://asc.fasb.org/extlink&oid=114873765&loc=SL114874048-224260

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The net change in the difference between the fair value and the carrying value, or in the comparative fair values, of derivative instruments, including options, swaps, futures, and forward contracts, held at each balance sheet date, that was included in earnings for the period.

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Derivatives and Risk Management - Narrative (Details) € in Millions, ¥ in Millions, $ in Millions, $ in Millions	1 Months Ended		9 Months Ended	12 Months Ended
	Aug. 31, 2018 USD ($)	Jan. 31, 2018 EUR (€)	Dec. 31, 2018 EUR (€)	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)	Dec. 31, 2018 JPY (¥)	Dec. 31, 2018 USD ($)	Sep. 01, 2018 EUR (€)	Apr. 30, 2018 USD ($)	Dec. 31, 2017 JPY (¥)	Dec. 31, 2017 USD ($)	Dec. 31, 2017 CAD ($)
Derivative [Line Items]
Held margin on hedge contract								$ 9
Posted margin on hedge contract												$ 43
Fuel hedge contracts
Derivative [Line Items]
Derivative losses					$ 81	$ 366
Foreign currency exchange contracts
Derivative [Line Items]
Gain on settlement of derivative	$ 18
Unrealized loss on derivative				$ 4
Designated as hedging instrument \| Fair value hedge \| Interest rate contracts
Derivative [Line Items]
Derivative, notional amount								$ 1,893		$ 1,600
Designated as hedging instrument \| Cash flow hedge \| Foreign currency exchange contracts
Derivative [Line Items]
Derivative, notional amount							¥ 6,934				¥ 23,512		$ 490
Not designated as hedging instrument \| Foreign currency exchange contracts
Derivative [Line Items]
Derivative, notional amount \| €			€ 397						€ 397
Not designated as hedging instrument \| Cash flow hedge \| Foreign currency exchange contracts
Derivative [Line Items]
Derivative, term of contract		3 years
Derivative, notional amount \| €		€ 375
Minimum \| Designated as hedging instrument \| Fair value hedge \| Interest rate contracts
Derivative [Line Items]
Derivative, term of contract			2 years
Maximum \| Designated as hedging instrument \| Fair value hedge \| Interest rate contracts
Derivative [Line Items]
Derivative, term of contract			9 years