Commitments and Contingencies - Employees (Details) $ in Millions		1 Months Ended	3 Months Ended	12 Months Ended
	Mar. 31, 2016	May 31, 2015	Jun. 30, 2016 USD ($)	Dec. 31, 2016 USD ($) employee_group airport	Dec. 31, 2015 USD ($) employee_group
Concentration Risk [Line Items]
Number of airports in which company operates | airport				59
Health Insurance Product Line
Concentration Risk [Line Items]
Accrued health care claims | $				$ 5.7	$ 3.7
Association of Flight Attendants (AFA-CWA)
Concentration Risk [Line Items]
Tentative collective bargaining agreement, contract term	5 years
Ratified Collective Bargaining Agreement, Incentive Payment | $			$ 9.6
International Association of Machinists and Aerospace Workers (IAMAW)
Concentration Risk [Line Items]
Tentative collective bargaining agreement, contract term		5 years
Number of airports in which company operates | airport				1
Unionized employees concentration risk | Number of employees (percent)
Concentration Risk [Line Items]
Union-represented employee groups | employee_group				4	4
Concentration of risk				73.00%	73.00%
Unionized employees concentration risk | Number of employees (percent) | Air Line Pilots Association, International (ALPA)
Concentration Risk [Line Items]
Concentration of risk				26.00%
Unionized employees concentration risk | Number of employees (percent) | Association of Flight Attendants (AFA-CWA)
Concentration Risk [Line Items]
Concentration of risk				42.00%
Unionized employees concentration risk | Number of employees (percent) | Transport Workers Union (TWU)
Concentration Risk [Line Items]
Concentration of risk				1.00%
Unionized employees concentration risk | Number of employees (percent) | International Association of Machinists and Aerospace Workers (IAMAW)
Concentration Risk [Line Items]
Concentration of risk				4.00%