OPERATING SEGMENT INFORMATION, ASSETS (Details) - USD ($) $ in Millions	Mar. 31, 2019	Dec. 31, 2018
Total assets	$ 12,640	$ 10,912
Alaska Airlines [Member]
Total assets	18,698	16,853
Horizon [Member]
Total assets	1,209	1,229
Parent [Member]
Total assets	$ (7,267)	$ (7,170)