ACQUISITION OF VIRGIN AMERICA, INC. (Details) - USD ($) $ / shares in Units, $ in Millions			12 Months Ended
		Dec. 14, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Business Acquisition [Line Items]
Revenue			$ 7,933	$ 5,931	$ 5,598
Net Income			1,034	814	848
Goodwill			1,943	1,934
Special items—merger-related costs and other			118	117
Virgin America Inc. [Member]
Business Acquisition [Line Items]
Percentage of interests acquired		100.00%
Business Acquisition, Share Price		$ 57
Business Combination, Consideration Transferred		$ 2,600
Goodwill		1,943
Intangible assets		141
Finite-lived intangible assets acquired		52
Special items—merger-related costs and other			118	117
Airport Gates [Member] | Virgin America Inc. [Member]
Business Acquisition [Line Items]
Finite-lived intangible assets acquired		$ 14
Finite-Lived intangible asset, useful Life		11 years
Credit Card Agreements [Member] | Virgin America Inc. [Member]
Business Acquisition [Line Items]
Finite-lived intangible assets acquired		$ 1
Finite-Lived intangible asset, useful Life		1 year
Customer Relationships [Member] | Virgin America Inc. [Member]
Business Acquisition [Line Items]
Finite-lived intangible assets acquired		$ 37
Finite-Lived intangible asset, useful Life		7 years
Airport Slots [Member] | Virgin America Inc. [Member]
Business Acquisition [Line Items]
Indefinite-lived intangible assets acquired		$ 89
Special Charges [Member]
Business Acquisition [Line Items]
Revenue	[1]		$ 0	$ 0	$ 0

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