Accrued Liabilities (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Payables and Accruals [Abstract]
Salaries and wages	$ 50,635	$ 54,578
Airport obligations	47,289	43,989
Federal excise and other passenger taxes and fees payable	43,860	42,064
Aircraft maintenance	41,781	30,233
Interest payable	15,168	8,499
Fuel	14,940	14,828
Aircraft and facility lease obligations	11,678	10,378
Other	23,781	21,442
Other current liabilities	$ 249,132	$ 226,011