Revenue Recognition - Passenger Revenue (Details) - USD ($) $ in Millions	3 Months Ended	6 Months Ended
Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Disaggregation of Revenue [Line Items]
Operating revenue	$ 12,536	$ 11,775	$ 23,008	$ 21,743
Passenger
Disaggregation of Revenue [Line Items]
Operating revenue	11,368	10,546	20,622	19,311
Ticket
Disaggregation of Revenue [Line Items]
Operating revenue	9,969	9,308	17,957	16,961
Loyalty travel awards
Disaggregation of Revenue [Line Items]
Operating revenue	751	680	1,442	1,298
Travel-related services
Disaggregation of Revenue [Line Items]
Operating revenue	$ 648	$ 558	$ 1,223	$ 1,052

Amount, excluding tax collected from customer, of revenue from satisfaction of performance obligation by transferring promised good or service to customer. Tax collected from customer is tax assessed by governmental authority that is both imposed on and concurrent with specific revenue-producing transaction, including, but not limited to, sales, use, value added and excise.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 4
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=118956577&loc=SL49130543-203045

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 5
-URI http://asc.fasb.org/extlink&oid=118956577&loc=SL49130545-203045

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration