INCOME TAXES - EFFECTIVE INCOME TAX RECONCILIATION (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Business Acquisition [Line Items]
U.S. federal tax rate	35.00%	35.00%	35.00%
Income before income tax	$ 1,207	$ 1,345	$ 1,312
Expected tax expense	422	471	459
Nondeductible expenses	5	20	4
State income taxes	29	28	19
State income sourcing	9	13	(15)
Tax law changes	(280)	0	0
Other—net	(12)	(1)	(3)
Income tax expense	$ 173	$ 531	$ 464
Effective tax rate	14.30%	39.50%	35.40%
Tax Cuts And Jobs Act Of 2017, Change In Tax Rate, Deferred Tax Asset, Income Tax Expense	$ 280
Virgin America Inc. [Member]
Business Acquisition [Line Items]
Nondeductible expenses		$ 39