Retirement Plans and Employee Stock Purchase Plans (Details) (USD $) In Millions, unless otherwise specified	1 Months Ended		2 Months Ended	12 Months Ended
	Dec. 31, 2007 Y	Nov. 30, 2007 Y	Dec. 31, 2010	Dec. 31, 2011 Y	Dec. 31, 2011 Minimum Y	Dec. 31, 2011 Maximum Y	Dec. 31, 2011 SkyWest Plan D Y	Dec. 31, 2010 SkyWest Plan	Dec. 31, 2009 SkyWest Plan	Dec. 31, 2011 Atlantic Southeast Plan Y D	Dec. 31, 2010 Atlantic Southeast Plan	Dec. 31, 2009 Atlantic Southeast Plan	Dec. 31, 2011 Atlantic Southeast Plan Minimum	Dec. 31, 2011 Atlantic Southeast Plan Maximum
Retirement Plans
Service period required to be completed to be eligible to participate in plan (in days)							90			90
Required age for an employee to be eligible to participate in plan (in years)							18			18
Percentage of employer matching contribution based on length of service							100.00%						20.00%	75.00%
Percentage of participant's compensation eligible for employer's matching contribution based upon length of service, threshold one							2.00%
Percentage of participant's compensation eligible for employer's matching contribution based upon length of service, threshold two							4.00%
Percentage of participant compensation eligible for employer's matching contribution based upon length of service, threshold three							6.00%
Company's combined contributions				$ 19.3			$ 14.4	$ 13.3	$ 11.8	$ 5.8	$ 5.2	$ 4.7
Maximum percentage of participant's total compensation eligible for employer matching contribution										6.00%
Minimum service period required to be completed for eight percent matching contribution by the employer (in years)										10
Maximum percentage of participant's total compensation eligible for employer matching contribution after requisite service period										8.00%
Percentage of vesting for plan participants' elective deferrals and rollover amounts										100.00%
Percentage of vesting of company matching contribution based on length of service													10.00%	100.00%
ExpressJet Plan
Total expense for the plan			0.6
Eligible age to provide medical bridge coverage (in years)					60	65
Minimum period of service required to be completed by retired employees for availing medical bridge coverage (in years)				10
Mandatory retirement age for commercial pilots (in years)	65	60
Company's combined contributions				$ 19.3			$ 14.4	$ 13.3	$ 11.8	$ 5.8	$ 5.2	$ 4.7