Accrued Liabilities (Details) - USD ($) $ in Thousands	Mar. 31, 2016	Dec. 31, 2015
Payables and Accruals [Abstract]
Federal excise and other passenger taxes and fees payable	$ 51,475	$ 38,254
Salaries and wages	44,193	34,123
Airport obligations	34,362	30,849
Aircraft and facility lease obligations	25,577	24,014
Aircraft maintenance	25,093	21,688
Interest payable	18,265	12,355
Fuel	7,529	7,084
Other	21,643	14,362
Other current liabilities	$ 228,137	$ 182,729