Nature of Operations and Summary of Significant Accounting Policies - Agreements (Details) - aircraft	1 Months Ended	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2017	Dec. 31, 2016
Agreements with other airlines
Number of aircraft held by entity			685
CRJ 200
Agreements with other airlines
Number of aircraft held by entity			215
Number of aircraft removed from service	76
CRJ 200 | Forecast
Agreements with other airlines
Number of aircraft removed from service		46
CRJ 200 | Sky West Airlines Inc
Agreements with other airlines
Number of aircraft under contract			22
CRJ 700
Agreements with other airlines
Number of aircraft held by entity			139
CRJ 700 | Forecast
Agreements with other airlines
Number of aircraft operated in the existing fleet		49
CRJ 900
Agreements with other airlines
Number of aircraft held by entity			64
E 175
Agreements with other airlines
Number of aircraft held by entity			86
ERJ 135
Agreements with other airlines
Number of aircraft held by entity			9
ERJ 145
Agreements with other airlines
Number of aircraft held by entity			158
ERJ 145 | Forecast
Agreements with other airlines
Number of aircraft removed from service		45
EMB 120
Agreements with other airlines
Number of aircraft held by entity			14
ERJ145/135 | Forecast
Agreements with other airlines
Number of aircraft removed from service		59
Delta Connection Agreements | Sky West Airlines Inc
Agreements with other airlines
Term of agreement			3 years 8 months 12 days
Delta Connection Agreements | ExpressJet
Agreements with other airlines
Term of agreement			2 years 9 months 18 days
Delta Connection Agreements | CRJ 200 | Sky West Airlines Inc
Agreements with other airlines
Number of aircraft under contract			50
Delta Connection Agreements | CRJ 200 | ExpressJet
Agreements with other airlines
Number of aircraft under contract			38
Delta Connection Agreements | CRJ 700 | Sky West Airlines Inc
Agreements with other airlines
Number of aircraft under contract			27
Delta Connection Agreements | CRJ 700 | ExpressJet
Agreements with other airlines
Number of aircraft under contract			35
Delta Connection Agreements | CRJ 900 | Sky West Airlines Inc
Agreements with other airlines
Number of aircraft under contract			36
Delta Connection Agreements | CRJ 900 | ExpressJet
Agreements with other airlines
Number of aircraft under contract			28
Delta Connection Agreements | E 175 | Forecast
Agreements with other airlines
Number of additional aircrafts into service		6
Delta Connection Agreements | E 175 | Sky West Airlines Inc
Agreements with other airlines
Number of aircraft under contract			13
Delta Connection Prorate Agreements | Sky West Airlines Inc
Agreements with other airlines
Term of agreement			30 days
Delta Connection Prorate Agreements | CRJ 200 | Sky West Airlines Inc
Agreements with other airlines
Number of aircraft under contract			21
United Express Agreements | Sky West Airlines Inc
Agreements with other airlines
Term of agreement			5 years 8 months 12 days
United Express Agreements | CRJ 200 | Sky West Airlines Inc
Agreements with other airlines
Number of aircraft under contract			53
United Express Agreements | CRJ 700 | Sky West Airlines Inc
Agreements with other airlines
Number of aircraft under contract			35
United Express Agreements | E 175 | Forecast
Agreements with other airlines
Number of additional aircrafts into service		7
United Express Agreements | E 175 | Sky West Airlines Inc
Agreements with other airlines
Number of aircraft under contract			58
United ERJ Agreements | ExpressJet
Agreements with other airlines
Term of agreement			10 months 24 days
United ERJ Agreements | ERJ 135 | ExpressJet
Agreements with other airlines
Number of aircraft under contract			5
United ERJ Agreements | ERJ 145 | ExpressJet
Agreements with other airlines
Number of aircraft under contract			140
United Express Prorate Agreement | Sky West Airlines Inc
Agreements with other airlines
Term of agreement			120 days
American Capacity Purchase Agreement | CRJ 200 | Sky West Airlines Inc
Agreements with other airlines
Number of aircraft under contract			9
American Capacity Purchase Agreement | CRJ 200 | ExpressJet
Agreements with other airlines
Number of aircraft under contract			11
American Capacity Purchase Agreement | CRJ 700 | Sky West Airlines Inc
Agreements with other airlines
Number of aircraft under contract			23
American Capacity Purchase Agreement | CRJ 700 | ExpressJet
Agreements with other airlines
Number of aircraft under contract			10
American Capacity Purchase Agreement | ERJ 145 | ExpressJet
Agreements with other airlines
Number of aircraft under contract			14
American Prorate Agreement | Sky West Airlines Inc
Agreements with other airlines
Term of agreement			120 days
American Prorate Agreement | ExpressJet
Agreements with other airlines
Term of agreement			120 days
American Prorate Agreement | CRJ 200 | Sky West Airlines Inc
Agreements with other airlines
Number of aircraft under contract			6
American Prorate Agreement | CRJ 200 | ExpressJet
Agreements with other airlines
Number of aircraft under contract			3
Alaska Capacity Purchase Agreement | E 175 | Forecast
Agreements with other airlines
Number of additional aircrafts into service		5
Alaska Capacity Purchase Agreement | E 175 | Sky West Airlines Inc
Agreements with other airlines
Number of aircraft under contract			15
American
Agreements with other airlines
Number of aircraft held by entity			76
American | CRJ 200
Agreements with other airlines
Number of aircraft held by entity			29
American | CRJ 700
Agreements with other airlines
Number of aircraft held by entity			33
American | ERJ 145
Agreements with other airlines
Number of aircraft held by entity			14
Aircraft in scheduled service
Agreements with other airlines
Number of aircraft held by entity			652
Aircraft in scheduled service | CRJ 200
Agreements with other airlines
Number of aircraft held by entity			213
Aircraft in scheduled service | CRJ 700
Agreements with other airlines
Number of aircraft held by entity			130
Aircraft in scheduled service | CRJ 900
Agreements with other airlines
Number of aircraft held by entity			64
Aircraft in scheduled service | E 175
Agreements with other airlines
Number of aircraft held by entity			86
Aircraft in scheduled service | ERJ 135
Agreements with other airlines
Number of aircraft held by entity			5
Aircraft in scheduled service | ERJ 145
Agreements with other airlines
Number of aircraft held by entity			154
Aircraft in scheduled service | ERJ145/135
Agreements with other airlines
Number of aircraft held by entity			159