INCOME TAXES - EFFECTIVE INCOME TAX RECONCILIATION (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Business Acquisition [Line Items]
U.S. federal tax rate	21.00%	35.00%	35.00%
Income before income tax	$ 585	$ 1,159	$ 1,316
Expected tax expense	123	406	461
Nondeductible expenses	9	5	20
State income taxes	21	28	27
State income sourcing	0	9	12
Tax law changes	(7)	(237)	0
Other—net	2	(12)	(1)
Income tax expense	$ 148	$ 199	$ 519
Effective tax rate	25.30%	17.20%	39.40%
Virgin America Inc. [Member]
Business Acquisition [Line Items]
Nondeductible expenses			$ 39