Commitments and Contingencies - Employees (Details) $ in Thousands	1 Months Ended	3 Months Ended
	Feb. 28, 2018	Mar. 31, 2019 USD ($) employee_group	Mar. 31, 2018 USD ($)	Dec. 31, 2018 USD ($)
Liability for Claims and Claims Adjustment Expense [Line Items]
Special charges		$ 0	$ 89,168
Air Line Pilots Association, International [Member]
Concentration Risk [Line Items]
Term of collective bargaining agreement	5 years
Health Insurance
Liability for Claims and Claims Adjustment Expense [Line Items]
Accrued health care claims		$ 5,100		$ 4,400
Pilots [Member]
Liability for Claims and Claims Adjustment Expense [Line Items]
Ratification Incentive			80,700
Adjustments for contractual provisions			8,500
Special charges			$ 89,200
Unionized Employees Concentration Risk [Member] | Number of Employees, Total [Member]
Concentration Risk [Line Items]
Number of union-represented employee groups | employee_group		5
Company's employees covered under collective bargaining agreements (as a percent)		79.00%
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)		45.00%
Unionized Employees Concentration Risk [Member] | Number of Employees, Total [Member] | Professional Airline Flight Control Association [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%
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)		3.00%