Accrued Liabilities (Details) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Payables and Accruals [Abstract]
Salaries, wages and benefits	$ 92,056	$ 89,163
Airport obligations	37,309	80,134
Federal excise and other passenger taxes and fees payable	22,947	65,312
Aircraft maintenance	21,615	38,099
Aircraft and facility lease obligations	21,163	20,656
Interest payable	17,871	16,941
Fuel	5,259	28,510
Other	28,793	34,706
Other current liabilities	$ 247,013	$ 373,521