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Summary of Significant Accounting Policies (Details) - USD ($) | 3 Months Ended | 12 Months Ended
--- | --- | ---
Jun. 30, 2016 | Mar. 31, 2016 | Dec. 31, 2015 | Sep. 30, 2015 | Dec. 31, 2016 | Dec. 31, 2015 | Dec. 31, 2014
Accounting Policies [Abstract] |  |  |  |  |  |  |  |
Inventory reserve for obsolescence |  |  |  | $ 47,000,000 |  | $ 57,000,000 | $ 47,000,000 |
Frequent Flier Liability, Current |  |  |  | 1,300,000,000 |  | 1,400,000,000 | 1,300,000,000 |
Capitalized computer software, net |  |  |  | 378,000,000 |  | 544,000,000 | 378,000,000 |
Computer software depreciation expense |  |  |  |  |  | 111,000,000 | 106,000,000 | $ 122,000,000
Capitalized computer software, Impairments |  |  |  |  |  | 0 | 0 | 0
Advertising costs |  |  |  |  |  | 232,000,000 | 218,000,000 | 207,000,000
Change in Accounting Estimate [Line Items] |  |  |  |  |  |  |  |
New Accounting Pronouncement or Change in Accounting Principle, Effect of Change on Operating Results |  | $ 137,000,000 | $ 115,000,000 | $ 124,000,000 | $ 303,000,000 | 544,000,000 | 427,000,000 |
Change in Accounting Estimate Financial Effect on Depreciation Expense, Depreciation Estimate |  |  |  |  |  | 123,000,000 |  |
Special revenue adjustment |  |  |  |  |  | 0 | 172,000,000 | 0
Change In Accounting Estimate Financial Effect On Depreciation Expense 2017 |  |  |  |  |  | 21,000,000 |  |
Change in Accounting Estimate Financial Effect on Passenger Revenue |  |  |  |  |  |  | 115,000,000 | 55,000,000
Change in accounting estimate, financial effect on net income, spoilage adjustment |  |  |  |  |  |  | $ 61,000,000 | $ 29,000,000
Change in accounting estimate,financial effect on earnings per share |  |  |  |  |  |  | $ 0.09 | $ 0.04
New Accounting Pronouncement or Change in Accounting Principle, Effect of Change on Net Income |  |  |  |  |  | $ 293,000,000 | $ 227,000,000 |
New Accounting Pronouncement or Change in Accounting Principle, Effect of Change on Basic Earnings Per Share |  | $ 0.12 | $ 0.10 | $ 0.10 | $ 0.24 | $ 0.47 | $ 0.34 |
New Accounting Pronouncement or Change in Accounting Principle, Effect of Change on Diluted Earnings Per Share |  | $ 0.11 | $ 0.09 | $ 0.10 | $ 0.24 | $ 0.46 | 0.34 |
Change in accounting estimate, financial effect on earnings per share diluted |  |  |  |  |  |  | $ 0.09 | $ 0.04
Change in Accounting Estimate, Financial Effect on Net Income, Depreciation Adjustment | [1] |  |  |  |  | $ (66,000,000) |  |
Change in Accounting Estimate, Financial Effect on Net Income Per Share, Depreciation Estimate |  |  |  |  |  | $ (0.11) |  |
ChangeinAccountingEstimateFinancialEffectonNetIncomePerShareDilutedDepreciationEstimate |  |  |  |  |  | $ (0.10) |  |
Acquired Finite-Lived Intangible Assets [Line Items] |  |  |  |  |  |  |  |
Gross carrying amount |  |  |  | $ 574,000,000 |  | $ 549,000,000 | $ 574,000,000 |
Weighted-average useful life (in years) |  |  |  |  |  | 13 years |  |
Accumulated amortization |  |  |  | 110,000,000 |  | $ 123,000,000 | 110,000,000 |
Amortization of intangible assets |  |  |  |  |  | 17,000,000 | 19,000,000 | $ 13,000,000
Impairment of Intangible Assets, Indefinite-lived (Excluding Goodwill) |  |  |  |  |  | 21,000,000 | 0 | $ 0
Finite-Lived Intangible Assets, Future Amortization Expense [Abstract] |  |  |  |  |  |  |  |
2017 |  |  |  |  |  | 13,000,000 |  |
2018 |  |  |  |  |  | 13,000,000 |  |
2019 |  |  |  |  |  | 13,000,000 |  |
2020 |  |  |  |  |  | 12,000,000 |  |
2021 |  |  |  |  |  | 12,000,000 |  |
Thereafter |  |  |  |  |  | 68,000,000 |  |
Fuel derivatives |  |  |  |  |  |  |  |
Accounting Policies [Abstract] |  |  |  |  |  |  |  |
Total collateral already posted aggregate fair value |  |  |  | 835,000,000 |  | 301,000,000 | 835,000,000 |
Other Noncurrent Liabilities | Fuel derivatives |  |  |  |  |  |  |  |
Accounting Policies [Abstract] |  |  |  |  |  |  |  |
Collateral Already Posted, Aggregate Fair Value |  |  |  | 600,000,000 |  | 0 | 600,000,000 |
Other Noncurrent Liabilities | Interest rate derivatives |  |  |  |  |  |  |  |
Accounting Policies [Abstract] |  |  |  |  |  |  |  |
Collateral Already Posted, Aggregate Fair Value |  |  |  | 0 |  | $ 0 | 0 |
Flight equipment |  |  |  |  |  |  |  |
Property, Plant and Equipment [Line Items] |  |  |  |  |  |  |  |
Minimum percentage of cost estimated residual value (in hundredths) |  |  |  |  |  | 2.00% |  |
Maximum percentage of cost estimated as residual value (in hundredths) |  |  |  |  |  | 20.00% |  |
Flight equipment | Minimum |  |  |  |  |  |  |  |
Property, Plant and Equipment [Line Items] |  |  |  |  |  |  |  |
Property, Plant, and Equipment Useful Life |  |  |  |  |  | 23 years |  |
Flight equipment | Maximum |  |  |  |  |  |  |  |
Property, Plant and Equipment [Line Items] |  |  |  |  |  |  |  |
Property, Plant, and Equipment Useful Life |  |  |  |  |  | 25 years |  |
Property, Plant and Equipment [Member] | Minimum |  |  |  |  |  |  |  |
Property, Plant and Equipment [Line Items] |  |  |  |  |  |  |  |
Property, Plant, and Equipment Useful Life |  |  |  |  |  | 5 years |  |
Property, Plant and Equipment [Member] | Maximum |  |  |  |  |  |  |  |
Property, Plant and Equipment [Line Items] |  |  |  |  |  |  |  |
Property, Plant, and Equipment Useful Life |  |  |  |  |  | 30 years |  |
Ground property and equipment |  |  |  |  |  |  |  |
Property, Plant and Equipment [Line Items] |  |  |  |  |  |  |  |
Minimum percentage of cost estimated residual value (in hundredths) |  |  |  |  |  | 0.00% |  |
Maximum percentage of cost estimated as residual value (in hundredths) |  |  |  |  |  | 10.00% |  |
AssetsConstructedForOthers |  |  |  |  |  |  |  |
Property, Plant and Equipment [Line Items] |  |  |  |  |  |  |  |
Minimum percentage of cost estimated residual value (in hundredths) |  |  |  |  |  | 17.00% |  |
Maximum percentage of cost estimated as residual value (in hundredths) |  |  |  |  |  | 25.00% |  |
AssetsConstructedForOthers | Minimum |  |  |  |  |  |  |  |
Property, Plant and Equipment [Line Items] |  |  |  |  |  |  |  |
Property, Plant, and Equipment Useful Life |  |  |  |  |  | 25 years |  |
AssetsConstructedForOthers | Maximum |  |  |  |  |  |  |  |
Property, Plant and Equipment [Line Items] |  |  |  |  |  |  |  |
Property, Plant, and Equipment Useful Life |  |  |  |  |  | 30 years |  |
Software | Minimum |  |  |  |  |  |  |  |
Property, Plant and Equipment [Line Items] |  |  |  |  |  |  |  |
Property, Plant, and Equipment Useful Life |  |  |  |  |  | 5 years |  |
Software | Maximum |  |  |  |  |  |  |  |
Property, Plant and Equipment [Line Items] |  |  |  |  |  |  |  |
Property, Plant, and Equipment Useful Life |  |  |  |  |  | 15 years |  |
Passenger Revenue |  |  |  |  |  |  |  |
Change in Accounting Estimate [Line Items] |  |  |  |  |  |  |  |
New Accounting Pronouncement or Change in Accounting Principle, Effect of Change on Operating Results |  |  |  |  |  | $ (250,000,000) | (89,000,000) |
Other Revenue [Member] |  |  |  |  |  |  |  |
Change in Accounting Estimate [Line Items] |  |  |  |  |  |  |  |
New Accounting Pronouncement or Change in Accounting Principle, Effect of Change on Operating Results |  |  |  |  |  | 794,000,000 | 344,000,000 |
Special Revenue Adjustment [Member] |  |  |  |  |  |  |  |
Change in Accounting Estimate [Line Items] |  |  |  |  |  |  |  |
New Accounting Pronouncement or Change in Accounting Principle, Effect of Change on Operating Results |  |  |  |  |  | 0 | 172,000,000 |
Customer relationships/marketing agreements |  |  |  |  |  |  |  |
Acquired Finite-Lived Intangible Assets [Line Items] |  |  |  |  |  |  |  |
Gross carrying amount of finite-lived intangible assets |  |  |  | 38,000,000 |  | $ 38,000,000 | 38,000,000 |
Weighted-average useful life (in years) |  |  |  |  |  | 9 years |  |
Accumulated amortization |  |  |  | 30,000,000 |  | $ 32,000,000 | 30,000,000 |
Trademarks/trade names |  |  |  |  |  |  |  |
Acquired Finite-Lived Intangible Assets [Line Items] |  |  |  |  |  |  |  |
Gross carrying amount of finite-lived intangible assets |  |  |  | 36,000,000 |  | $ 36,000,000 | 36,000,000 |
Weighted-average useful life (in years) |  |  |  |  |  | 6 years |  |
Accumulated amortization |  |  |  | 34,000,000 |  | $ 36,000,000 | 34,000,000 |
Owned domestic slots |  |  |  |  |  |  |  |
Acquired Finite-Lived Intangible Assets [Line Items] |  |  |  |  |  |  |  |
Gross carrying amount of indefinite-lived intangible assets | [2] |  |  | 303,000,000 |  | 295,000,000 | 303,000,000 |
Leased domestic slots (a) |  |  |  |  |  |  |  |
Acquired Finite-Lived Intangible Assets [Line Items] |  |  |  |  |  |  |  |
Gross carrying amount of finite-lived intangible assets | [2] |  |  | 17,000,000 |  | $ 0 | 17,000,000 |
Weighted-average useful life (in years) | [2] |  |  |  |  | 0 years |  |
Accumulated amortization | [2] |  |  | 3,000,000 |  | $ 0 | 3,000,000 |
Gate leasehold rights (b) |  |  |  |  |  |  |  |
Acquired Finite-Lived Intangible Assets [Line Items] |  |  |  |  |  |  |  |
Gross carrying amount of finite-lived intangible assets | [3] |  |  | 180,000,000 |  | $ 180,000,000 | 180,000,000 |
Weighted-average useful life (in years) | [3] |  |  |  |  | 15 years |  |
Accumulated amortization | [3] |  |  | $ 43,000,000 |  | $ 55,000,000 | $ 43,000,000 |
Unionized Employees concentration risk |  |  |  |  |  |  |  |
Concentration Risk [Line Items] |  |  |  |  |  |  |  |
The percentage of Company's employees that are unionized and covered by collective bargaining agreements (in hundredths) |  |  |  |  |  | 83.00% |  |
[1] | net of profitsharing benefit
[2] | The Company recorded a $21 million impairment associated with owned and leased slots at Newark Liberty International Airport as a result of the FAA announcement, in April 2016, that this airport was being changed to a Level 2 schedule-facilitated airport from its previous designation as Level 3.
[3] | Intangible assets primarily consist of acquired leasehold rights to certain airport owned gates, takeoff and landing slots (a “slot” is the right of an air carrier, pursuant to regulations of the FAA, to operate a takeoff or landing at a specific time at certain airports) at certain domestic slot-controlled airports, and certain intangible assets acquired.

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