Impact of the COVID-19 Pandemic (Details) $ in Millions			1 Months Ended	3 Months Ended	12 Months Ended
	Apr. 24, 2020 USD ($)	Apr. 23, 2020 USD ($)	Apr. 30, 2020 item	Mar. 31, 2020 USD ($) aircraft	Dec. 31, 2020 aircraft
Unusual Risk or Uncertainty [Line Items]
Liquid Assets				$ 644.1
Cash and Marketable Securities				577.9
Line of credit facility, reduction of amount available				66.2
Maximum borrowing capacity				$ 75.0
Forecast
Unusual Risk or Uncertainty [Line Items]
Number of daily departures | item			2,500
Minimum | Subsequent event | COVID-19
Unusual Risk or Uncertainty [Line Items]
Number of daily departures | item			800
Maximum | Subsequent event
Unusual Risk or Uncertainty [Line Items]
CARES Act, secured loans to airline industry	$ 25,000.0
Maximum | Subsequent event | COVID-19
Unusual Risk or Uncertainty [Line Items]
Number of daily departures | item			900
PSP agreement | Subsequent event
Unusual Risk or Uncertainty [Line Items]
Grants receivable		$ 438.0
Grants Received Percentage		50.00%
Loan Program | Subsequent event
Unusual Risk or Uncertainty [Line Items]
Maximum borrowing capacity	$ 497.0
Sky West Airlines Inc | American Prorate Agreement
Unusual Risk or Uncertainty [Line Items]
Number of aircraft | aircraft				7
CRJ 200 | Sky West Airlines Inc | Delta Connection Agreement
Unusual Risk or Uncertainty [Line Items]
Number of aircraft | aircraft				55
CRJ 200 | Sky West Airlines Inc | American Prorate Agreement | Forecast
Unusual Risk or Uncertainty [Line Items]
Number of aircraft removed from service | aircraft					7