Flying Agreements Revenue and Airport Customer Service and Other Revenue (Details) $ in Thousands	3 Months Ended			9 Months Ended		27 Months Ended
	Sep. 30, 2018 USD ($)	Sep. 30, 2017 USD ($)		Sep. 30, 2018 USD ($) aircraft item	Sep. 30, 2017 USD ($)	Dec. 31, 2020 aircraft
Agreements with other airlines
Percentage of ASMs flown under fixed-fee arrangements				84.30%
Percentage of ASMs flown under pro-rate arrangements				15.70%
Revenues [Abstract]
Operating revenues | $	$ 829,275	$ 812,673	[1]	$ 2,418,190	$ 2,351,351
Sky West Airlines Inc | Delta Connection Prorate Agreement
Revenues [Abstract]
Term of agreement				30 days
Sky West Airlines Inc | United Express Prorate Agreement
Revenues [Abstract]
Term of agreement				120 days
Sky West Airlines Inc | American Prorate Agreement
Revenues [Abstract]
Term of agreement				120 days
CRJ 200 | Sky West Airlines Inc | Delta Connection Agreements
Revenues [Abstract]
Number of aircraft				65
CRJ 200 | Sky West Airlines Inc | Delta Connection Prorate Agreement
Revenues [Abstract]
Number of aircraft				29
CRJ 200 | Sky West Airlines Inc | United Express Agreements
Revenues [Abstract]
Number of aircraft				61
CRJ 200 | Sky West Airlines Inc | United Express Prorate Agreement
Revenues [Abstract]
Number of aircraft				23
CRJ 200 | Sky West Airlines Inc | American Prorate Agreement
Revenues [Abstract]
Number of aircraft				7
CRJ 200 | ExpressJet
Revenues [Abstract]
Number of aircraft				20
Term of agreement				3 years
CRJ 700 | Sky West Airlines Inc | Delta Connection Agreements
Revenues [Abstract]
Number of aircraft				25
CRJ 700 | Sky West Airlines Inc | United Express Agreements
Revenues [Abstract]
Number of aircraft				19
CRJ 700 | Sky West Airlines Inc | American Capacity Purchase Agreement
Revenues [Abstract]
Number of aircraft				42
CRJ 700 | ExpressJet | Delta Connection Agreements
Revenues [Abstract]
Number of aircraft				12
CRJ 700 | ExpressJet | Alaska Capacity Purchase Agreement
Revenues [Abstract]
Number of aircraft				16
CRJ 700 | Delta
Revenues [Abstract]
Number of aircraft				20
CRJ 700 | American
Revenues [Abstract]
Term of agreement				4 years
Number of additional aircraft placed into service				20
CRJ 700 | United
Revenues [Abstract]
Number of aircraft				19
CRJ 900 | Sky West Airlines Inc | Delta Connection Agreements
Revenues [Abstract]
Number of aircraft				37
CRJ 900 | Delta | Forecast
Revenues [Abstract]
Number of additional aircraft placed into service						20
E 175 | Minimum
Revenues [Abstract]
Number of seats on aircraft | item				70
E 175 | Maximum
Revenues [Abstract]
Number of seats on aircraft | item				76
E 175 | Sky West Airlines Inc | Delta Connection Agreements
Revenues [Abstract]
Number of aircraft				41
E 175 | Sky West Airlines Inc | United Express Agreements
Revenues [Abstract]
Number of aircraft				65
E 175 | Sky West Airlines Inc | Alaska Capacity Purchase Agreement
Revenues [Abstract]
Number of aircraft				32
E 175 | Alaska
Revenues [Abstract]
Number of additional aircraft placed into service				3
Number of additional aircraft placed into service, deferred				3
E 175 | Delta
Revenues [Abstract]
Number of additional aircraft placed into service				8
ERJ 145 | ExpressJet | United Express Agreements
Revenues [Abstract]
Number of aircraft				100
Flying agreements
Revenues [Abstract]
Operating revenues | $	816,057	800,965	[1]	$ 2,377,659	2,317,218
Flight operations
Revenues [Abstract]
Operating revenues | $	472,952	462,832		1,404,801	1,367,901
Aircraft rentals
Revenues [Abstract]
Operating revenues | $	208,813	213,967		599,188	621,099
Prorate agreements
Revenues [Abstract]
Operating revenues | $	$ 134,292	$ 124,166		$ 373,670	$ 328,218

[1] Amounts adjusted due to the adoption of Accounting Standards Update No. 2014-09, Revenue from Contracts with Customers (Topic 606). See Note 1 to the financial statements contained in Part I, Item 1 of this report for additional information.