Commitments and Contingencies - Employees (Details) $ in Millions		1 Months Ended	3 Months Ended
	Mar. 31, 2016 USD ($) airport	May. 31, 2015	Mar. 31, 2016 USD ($) airport	Dec. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)
Concentration Risk [Line Items]
Number of airports in which entity operates | airport	56		56
Association of Flight Attendants [Member]
Concentration Risk [Line Items]
Tentative collective bargaining agreement, contract term	5 years
Accrued Bonuses	$ 9.6		$ 9.6		$ 1.2
Increase in accrued bonuses			$ 8.4
International Association Of Machinists And Aerospace Workers (IAM) [Member]
Concentration Risk [Line Items]
Interim collective bargaining agreement, contract term		5 years
Number of airports in which entity operates | airport	1		1
Health Insurance [Member]
Liability for Claims and Claims Adjustment Expense [Line Items]
Accrued health care claims	$ 4.2		$ 4.2	$ 4.3
Unionized Employees Concentration Risk [Member] | Number of Employees, Total [Member]
Concentration Risk [Line Items]
Company's employees covered under collective bargaining agreements (as a percent)			74.00%
Unionized Employees Concentration Risk [Member] | Number of Employees, Total [Member] | Air Line Pilots Association, International [Member]
Concentration Risk [Line Items]
Company's employees covered under collective bargaining agreements (as a percent)			26.00%
Unionized Employees Concentration Risk [Member] | Number of Employees, Total [Member] | Association of Flight Attendants [Member]
Concentration Risk [Line Items]
Company's employees covered under collective bargaining agreements (as a percent)			43.00%
Unionized Employees Concentration Risk [Member] | Number of Employees, Total [Member] | Transport Workers Union [Member]
Concentration Risk [Line Items]
Company's employees covered under collective bargaining agreements (as a percent)			1.00%
Unionized Employees Concentration Risk [Member] | Number of Employees, Total [Member] | International Association Of Machinists And Aerospace Workers (IAM) [Member]
Concentration Risk [Line Items]
Company's employees covered under collective bargaining agreements (as a percent)			4.00%