Commitments and Contingencies (Details) $ in Thousands	3 Months Ended	6 Months Ended
	Jun. 30, 2015 USD ($) aircraft	Jun. 30, 2015 USD ($) aircraft	Dec. 31, 2014 USD ($)
Commitments and Contingencies
Number of aircraft leased by the entity | aircraft		510
Supply Commitment [Line Items]
Long-term debt amount	$ 25,000	$ 25,000
Debt Instrument, Term		4 years
Interest rate (as a percent)	3.30%	3.30%
Future minimum rental payments required under operating leases
April through December 2015	$ 131,544	$ 131,544
2016	268,307	268,307
2017	201,693	201,693
2018	157,203	157,203
2019	120,257	120,257
Thereafter	453,812	453,812
Total future lease obligations	$ 1,332,816	$ 1,332,816
E 175
Supply Commitment [Line Items]
Number of aircrafts committed to purchase | aircraft		17
Number of aircraft delivered | aircraft	9	18
Debt issued to purchase of aircraft	$ 204,500	$ 407,600
Debt Instrument, Term		12 years
E 175 | Minimum
Supply Commitment [Line Items]
Interest rate (as a percent)	3.40%	3.40%
E 175 | Maximum
Supply Commitment [Line Items]
Interest rate (as a percent)	3.90%	3.90%
EMB 120
Future minimum rental payments required under operating leases
Total future lease obligations	$ 2,900	$ 2,900	$ 3,800