Accrued Liabilities (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2014	Dec. 31, 2013
Payables and Accruals [Abstract]
Federal excise and other passenger taxes and fees payable	$ 37,101	$ 26,979
Aircraft maintenance	27,324	36,165
Salaries and wages	24,962	26,174
Federal and state income tax payable	18,859	794
Airport expenses	16,515	17,109
Fuel	10,887	13,819
Aircraft and facility rent	8,449	7,993
Other	17,075	16,229
Other current liabilities	$ 161,172	$ 145,262