Special Charges (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2019 USD ($) aircraft	Dec. 31, 2018 USD ($) aircraft	Dec. 31, 2017 USD ($) aircraft_engine aircraft
Property, Plant and Equipment [Line Items]
Purchase of property and equipment	$ 192,437	$ 606,971	$ 628,881
Special charges	717	88,921	12,629
Special charges, non-operating	$ 0	$ 90,357	$ 0
Spare engines
Property, Plant and Equipment [Line Items]
Number of previously leased aircraft purchased off lease | aircraft	2
Aircraft
Property, Plant and Equipment [Line Items]
Number of previously leased aircraft purchased off lease | aircraft			1
Purchase of property and equipment			$ 12,600
Value of noncash consideration			7,400
Fair value of assets acquired			11,900
Special charges			7,900
Aircraft | Other Non-Cash Items
Property, Plant and Equipment [Line Items]
Value of noncash consideration			200
Airbus A319 | Aircraft
Property, Plant and Equipment [Line Items]
Purchase price			$ 20,000
Spare engines | Spare engines
Property, Plant and Equipment [Line Items]
Number of previously leased aircraft purchased off lease | aircraft_engine			1
Purchase price			$ 8,100
Purchase of property and equipment			3,800
Value of noncash consideration			4,300
Fair value of assets acquired			3,100
Special charges			4,800
Spare engines | Spare engines | Other Non-Cash Items
Property, Plant and Equipment [Line Items]
Value of noncash consideration			$ 200
Capital Lease Obligations | Airbus A319
Property, Plant and Equipment [Line Items]
Number of aircraft purchased | aircraft		14
Consideration transferred		$ 285,000
Pilots
Property, Plant and Equipment [Line Items]
Ratification Incentive		80,200
Collective bargaining agreement, contractual provision adjustments		8,500
Special charges		$ 88,700