Commitments and Contingencies - Schedule of Future Aircraft Operating Leases (Details)	Dec. 31, 2014 aircraft
Long-term Purchase Commitment [Line Items]
2015	15
2016	16
2017	18
2018	13
2019	13
2020	13
2021	18
Total future aircraft to be received	106
A320 | Airbus
Long-term Purchase Commitment [Line Items]
2015	8
2016	3
2017	8
2018	2
Total future aircraft to be received	21
A320NEO | Airbus
Long-term Purchase Commitment [Line Items]
2018	6
2019	3
2020	13
2021	18
Total future aircraft to be received	40
A320NEO | Third-Party Lessor
Long-term Purchase Commitment [Line Items]
2015	1
2016	4
Total future aircraft to be received	5
A321 | Airbus
Long-term Purchase Commitment [Line Items]
2015	6
2016	9
2017	10
2018	5
Total future aircraft to be received	30
A321NEO | Airbus
Long-term Purchase Commitment [Line Items]
2019	10
Total future aircraft to be received	10