Commitments and Contingencies - Employees (Details) $ in Millions		1 Months Ended		3 Months Ended		9 Months Ended
	Mar. 31, 2016	May 31, 2016	May 31, 2015	Sep. 30, 2016 USD ($) airport	Jun. 30, 2016 USD ($)	Sep. 30, 2016 USD ($) airport	Dec. 31, 2015 USD ($)
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
Compensation | $					$ 9.6
Ratified Collective Bargaining Agreement, Contract Term		5 years
International Association Of Machinists And Aerospace Workers (IAM) [Member]
Concentration Risk [Line Items]
Tentative 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 | $				$ 4.6		$ 4.6	$ 3.7
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)						72.00%
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)				42.00%
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)				3.00%