Commitments and Contingencies - Employees (Details) (USD $) In Millions, unless otherwise specified	1 Months Ended	12 Months Ended
	Aug. 31, 2014	Dec. 31, 2014	Dec. 31, 2013 employee_group	Jul. 08, 2014 employee
Concentration Risk [Line Items]
Union-represented employee groups		4	3
Number of airports in which company operates		56
Health Insurance Product Line
Concentration Risk [Line Items]
Accrued health care claims		3.1	2.1
Ramp Service Agents
Concentration Risk [Line Items]
Number of employees				250
International Association of Machinists and Aerospace Workers (IAM)
Concentration Risk [Line Items]
Number of airports in which company operates		4
Association of Flight Attendants (AFA-CWA)
Concentration Risk [Line Items]
Tentative collective bargaining agreement, contract term	5 years
Unionized employees concentration risk | Number of employees (percent)
Concentration Risk [Line Items]
Union-represented employee groups			3
Concentration of risk		67.00%	59.00%
Unionized employees concentration risk | Number of employees (percent) | International Association of Machinists and Aerospace Workers (IAM)
Concentration Risk [Line Items]
Concentration of risk		6.00%
Unionized employees concentration risk | Number of employees (percent) | Air Line Pilots Association, International (ALPA)
Concentration Risk [Line Items]
Concentration of risk		25.00%
Unionized employees concentration risk | Number of employees (percent) | Association of Flight Attendants (AFA-CWA)
Concentration Risk [Line Items]
Concentration of risk		35.00%
Unionized employees concentration risk | Number of employees (percent) | Transport Workers Union (TWU)
Concentration Risk [Line Items]
Concentration of risk		1.00%