OPERATING SEGMENT INFORMATION, ASSETS (Details) - USD ($) $ in Millions	Jun. 30, 2018	Dec. 31, 2017
Total assets	$ 11,055	$ 10,746
Alaska Airlines [Member]
Total assets	15,334	16,663
Horizon [Member]
Total assets	1,039	929
Parent [Member]
Total assets	$ (5,318)	$ (6,846)