Segment Reporting (Details) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2020 USD ($)	Sep. 30, 2020 USD ($)	Jun. 30, 2020 USD ($)	Mar. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)	Sep. 30, 2019 USD ($)	Jun. 30, 2019 USD ($)	Mar. 31, 2019 USD ($)	Dec. 31, 2020 USD ($) segment	Dec. 31, 2019 USD ($) segment	Dec. 31, 2018 USD ($)
Segment Reporting
Number of operating segments | segment										3
Number of reporting segments | segment									2
Operating revenues	$ 589,638	$ 457,493	$ 350,039	$ 729,936	$ 743,591	$ 760,295	$ 744,383	$ 723,694	$ 2,127,106	$ 2,971,963	$ 3,221,679
Operating expense									2,018,304	2,459,705	2,747,399
Depreciation and amortization expense									474,959	368,098	334,589
Special items								$ 21,900		21,869
Interest expense									123,173	127,755	120,409
Segment profit (loss)									(14,371)	384,503	353,871
Total assets	6,887,622				6,657,129				6,887,622	6,657,129	6,313,212
Capital expenditures (including non-cash)									460,483	846,470	1,156,276
SkyWest Airlines
Segment Reporting
Operating revenues									1,636,762	2,478,681	2,346,251
Operating expense									1,716,808	2,214,632	2,022,560
Depreciation and amortization expense									221,216	168,246	155,511
Special items										18,508
Interest expense									12,381	13,525	17,021
Segment profit (loss)									(92,427)	250,524	306,670
Total assets	2,804,259				2,728,964				2,804,259	2,728,964	2,531,707
Capital expenditures (including non-cash)									124,825	270,191	149,731
ExpressJet Airlines Inc
Segment Reporting
Operating revenues										24,050	564,202
Operating expense										28,690	577,608
Depreciation and amortization expense										971	37,290
Special items										3,361
Interest expense											2,340
Segment profit (loss)										(4,640)	(15,746)
Total assets											279,303
Capital expenditures (including non-cash)											10,137
SkyWest Leasing
Segment Reporting
Operating revenues									490,344	469,232	311,226
Operating expense									301,496	216,383	147,231
Depreciation and amortization expense									253,743	198,881	141,788
Interest expense									110,792	114,230	101,048
Segment profit (loss)									78,056	138,619	62,947
Total assets	$ 4,083,363				$ 3,928,165				4,083,363	3,928,165	3,502,202
Capital expenditures (including non-cash)									$ 335,658	$ 576,279	$ 996,408