Summary of Significant Accounting Policies (Details) - USD ($) $ in Millions	Jan. 01, 2018	Sep. 30, 2017
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Available-for-sale equity securities, accumulated gross unrealized gain		$ 49
ASU No. 2014-09 \| Scenario, Forecast
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Expected increase in passenger revenue upon adoption of new accounting standard	$ 2,000
Expected decrease in other revenue upon adoption of new accounting standard	$ 2,000

New Accounting Pronouncement Or Change In Accounting Principle, Expected Increase (Decrease) In Other Revenue

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- Definition

New Accounting Pronouncement Or Change In Accounting Principle, Expected Increase (Decrease) In Passenger Revenue

+ References

No definition available.

+ Details

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- Definition

Amount before tax of unrealized gain in accumulated other comprehensive income (AOCI) on investments in equity securities classified as available-for-sale.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=82897076&loc=d3e27161-111563

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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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