OPERATING SEGMENT INFORMATION, ASSETS (Details) - USD ($) $ in Millions	Sep. 30, 2018	Dec. 31, 2017
Total assets	$ 10,893	$ 10,746
Alaska Airlines [Member]
Total assets	14,725	16,663
Horizon [Member]
Total assets	1,037	929
Parent [Member]
Total assets	$ (4,869)	$ (6,846)