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Flying Agreements Revenue and Lease, Airport Services and Other Revenues - Flying Agreements (Details) $ in Thousands	3 Months Ended		6 Months Ended	12 Months Ended
	Mar. 31, 2020 USD ($) aircraft	Mar. 31, 2019 USD ($)	Jun. 30, 2020 USD ($) aircraft	Dec. 31, 2020 USD ($) aircraft	Dec. 31, 2019 USD ($)
Agreements with other airlines
Percentage of ASMs flown under fixed-fee arrangements	85.90%
Percentage of ASMs flown under pro-rate arrangements	14.10%
Revenues [Abstract]
Operating revenues	$ 729,936	$ 723,694
Rental income under operating leases
Operating lease revenue	10,546	9,058
Future minimum rental income
April 2020 through December 2020	23,484
2021	27,849
2022	27,606
2023	24,704
2024	24,396
Thereafter	87,235
Total	215,274
Property and equipment and related assets	5,393,738				$ 5,394,681
Balance	15,388		$ 15,388	$ 15,388
Additions to credit loss reserve	3,756
Balance	$ 19,144
Sky West Airlines Inc \| Delta Connection Prorate Agreement
Future minimum rental income
Number of aircraft \| aircraft	27
Agreement term	30 days
Sky West Airlines Inc \| United Express Prorate Agreement
Future minimum rental income
Number of aircraft \| aircraft	31
Agreement term	120 days
Sky West Airlines Inc \| American Prorate Agreement
Future minimum rental income
Number of aircraft \| aircraft	7
Agreement term	120 days
Third Party Lease
Future minimum rental income
Property and equipment and related assets	$ 154,100
CRJ 200 \| Sky West Airlines Inc \| Delta Connection Agreement
Future minimum rental income
Number of aircraft \| aircraft	55
Number of aircraft parked and stored \| aircraft	36
Additional depreciation	$ 15,000
Number of aircraft leased \| aircraft	19
CRJ 200 \| Sky West Airlines Inc \| United Express Agreements
Future minimum rental income
Number of aircraft \| aircraft	70
CRJ 200 \| Sky West Airlines Inc \| Forecast \| Delta Connection Agreement
Future minimum rental income
Number of aircraft parked and stored \| aircraft				36
Additional depreciation				$ 29,100
CRJ 700 \| American Capacity Purchase Agreement
Future minimum rental income
Number of aircraft \| aircraft	61
Number of aircraft to be placed in service \| aircraft	9
Total number of aircraft operated \| aircraft	70
CRJ 700 \| Sky West Airlines Inc \| Delta Connection Agreement
Future minimum rental income
Number of aircraft \| aircraft	8
CRJ 700 \| Sky West Airlines Inc \| United Express Agreements
Future minimum rental income
Number of aircraft \| aircraft	19
CRJ 900 \| Sky West Airlines Inc \| Delta Connection Agreement
Future minimum rental income
Number of aircraft \| aircraft	43
CRJ 900 \| Sky West Airlines Inc \| Delta Connection Prorate Agreement
Future minimum rental income
Number of aircraft to be placed in service \| aircraft	1
Agreement term	9 years
E175 \| Sky West Airlines Inc \| Delta Connection Agreement
Future minimum rental income
Number of aircraft \| aircraft	62
E175 \| Sky West Airlines Inc \| Delta Connection Prorate Agreement
Future minimum rental income
Number of aircraft to be placed in service \| aircraft	6
E175 \| Sky West Airlines Inc \| United Express Agreements
Future minimum rental income
Number of aircraft \| aircraft	69
E175 \| Sky West Airlines Inc \| American Prorate Agreement
Future minimum rental income
Number of aircraft to be placed in service \| aircraft	20
E175 \| Sky West Airlines Inc \| Forecast \| Delta Connection Prorate Agreement
Future minimum rental income
Number of aircraft to be placed in service \| aircraft			3
Current assets
Future minimum rental income
Gross receivables current	$ 42,000
Other noncurrent assets
Future minimum rental income
Gross receivables Non-current	76,700
Flying agreements
Revenues [Abstract]
Operating revenues	709,494	700,001
Flight operations
Revenues [Abstract]
Operating revenues	366,409	386,545
Aircraft lease
Revenues [Abstract]
Operating revenues	242,734	207,381
Prorate agreements
Revenues [Abstract]
Operating revenues	100,351	106,075
Airport customer service revenue
Revenues [Abstract]
Operating revenues	9,896	14,635
Airport customer service and other
Revenues [Abstract]
Operating revenues	$ 20,442	$ 23,693