Revenue - Roll Forward of Frequent Flyer Deferred Revenue (Details) - Deferred Revenue for Miles in Loyalty Program - USD ($) $ in Millions	3 Months Ended
Mar. 31, 2019	Mar. 31, 2018
Frequent Flyer Deferred Revenue [Roll Forward]
Total Frequent flyer deferred revenue - beginning balance	$ 5,005	$ 4,783
Miles awarded	607	603
Travel miles redeemed (Passenger revenue)	(438)	(409)
Non-travel miles redeemed (Other operating revenue)	(36)	(40)
Total Frequent flyer deferred revenue - ending balance	$ 5,138	$ 4,937

Amount of obligation to transfer good or service to customer for which consideration has been received or is receivable.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=82913815&loc=SL49130532-203044

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 8
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=82913847&loc=SL49130549-203045

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 45
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=82913815&loc=SL49130531-203044

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