OPERATING SEGMENT INFORMATION, ASSETS (Details) - USD ($) $ in Millions	Mar. 31, 2018	Dec. 31, 2017
Total assets	$ 10,848	$ 10,746
Alaska Airlines [Member]
Total assets	15,088	16,663
Horizon [Member]
Total assets	945	929
Parent [Member]
Total assets	$ (5,185)	$ (6,846)