Summary of Significant Accounting Policies (Details Textual) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Finite-Lived Intangible Assets [Line Items]
Aircraft Maintenance, Materials, and Repairs	$ 619	$ 625	$ 622
Maintenance service agreements, Minimum	10 years
Maintenance service agreements, Maximum	15 years
Advertising expense	$ 66	72	66
Deferred income taxes	1,251	1,112
Computer Software, Intangible Asset [Member]
Finite-Lived Intangible Assets [Line Items]
Capitalized Computer Software, Net	102	96
Amortization expense	52	$ 46	$ 41
Estimated Amortization expense related to computer software, Year one	35
Estimated Amortization expense related to computer software, Year two	26
Estimated Amortization expense related to computer software, Year three	22
Estimated Amortization expense related to computer software, Year four	15
Estimated Amortization expense related to computer software, Year five	4
High Density Airports, Take-Off and Landing Slots [Member]
Finite-Lived Intangible Assets [Line Items]
Intangible Assets, Net (Excluding Goodwill)	$ 139

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Amount charged to advertising expense for the period, which are expenses incurred with the objective of increasing revenue for a specified brand, product or product line.

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Maintenance costs incurred and directly related to services rendered by an entity during the reporting period. Includes the cost of inspections and repairs, materials and routine maintenance costs for all aircraft and engines.

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The aggregate expense charged against earnings to allocate the cost of intangible assets (nonphysical assets not used in production) in a systematic and rational manner to the periods expected to benefit from such assets. As a noncash expense, this element is added back to net income when calculating cash provided by or used in operations using the indirect method.

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The carrying amount of capitalized computer software costs net of accumulated amortization as of the balance sheet date.

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Amount, after deferred tax asset, of deferred tax liability attributable to taxable differences, with jurisdictional netting and classified as noncurrent.

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Amount of amortization expense for assets, excluding financial assets and goodwill, lacking physical substance with a finite life expected to be recognized during the fifth fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

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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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Sum of the carrying amounts of all intangible assets, excluding goodwill, as of the balance sheet date, net of accumulated amortization and impairment charges.

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