Nature of Operations and Summary of Significant Accounting Policies - Aircraft Fleet (Details)	12 Months Ended
	Dec. 31, 2016 item aircraft
Agreements with other airlines
Number of daily departures to different destinations | item	3,160
Number of aircraft held by entity	685
CRJ 200
Agreements with other airlines
Number of aircraft held by entity	215
CRJ 700
Agreements with other airlines
Number of aircraft held by entity	139
CRJ 900
Agreements with other airlines
Number of aircraft held by entity	64
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
E 175
Agreements with other airlines
Number of aircraft held by entity	86
EMB 120
Agreements with other airlines
Number of aircraft held by entity	14
United
Agreements with other airlines
Number of aircraft held by entity	313
Percentage of aggregate capacity operated	52.20%
United | CRJ 200
Agreements with other airlines
Number of aircraft held by entity	75
United | CRJ 700
Agreements with other airlines
Number of aircraft held by entity	35
United | ERJ 135
Agreements with other airlines
Number of aircraft held by entity	5
United | ERJ 145
Agreements with other airlines
Number of aircraft held by entity	140
United | E 175
Agreements with other airlines
Number of aircraft held by entity	58
Delta
Agreements with other airlines
Number of aircraft held by entity	248
Percentage of aggregate capacity operated	36.50%
Delta | CRJ 200
Agreements with other airlines
Number of aircraft held by entity	109
Delta | CRJ 700
Agreements with other airlines
Number of aircraft held by entity	62
Delta | CRJ 900
Agreements with other airlines
Number of aircraft held by entity	64
Delta | E 175
Agreements with other airlines
Number of aircraft held by entity	13
American
Agreements with other airlines
Number of aircraft held by entity	76
Percentage of aggregate capacity operated	6.30%
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
Alaska
Agreements with other airlines
Number of aircraft held by entity	15
Percentage of aggregate capacity operated	5.00%
Alaska | E 175
Agreements with other airlines
Number of aircraft held by entity	15
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 | 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 | E 175
Agreements with other airlines
Number of aircraft held by entity	86
Subleased to an un-affiliated entity
Agreements with other airlines
Number of aircraft held by entity	2
Subleased to an un-affiliated entity | CRJ 200
Agreements with other airlines
Number of aircraft held by entity	2
Other
Agreements with other airlines
Number of aircraft held by entity	31
Other | CRJ 700
Agreements with other airlines
Number of aircraft held by entity	9
Other | ERJ 135
Agreements with other airlines
Number of aircraft held by entity	4
Other | ERJ 145
Agreements with other airlines
Number of aircraft held by entity	4
Other | EMB 120
Agreements with other airlines
Number of aircraft held by entity	14