Accrued Liabilities (Details) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012
Payables and Accruals [Abstract]
Federal excise and other passenger taxes and fees payable	$ 34,748	$ 23,401
Aircraft maintenance	24,331	22,319
Salaries and wages	21,942	21,057
Airport expenses	18,095	16,024
Fuel	14,697	11,219
Aircraft and facility rent	8,065	8,020
Fuel derivatives	8,049	0
Tax receivable agreement	7,979	7,987
Other	13,610	11,287
Accrued liabilities	$ 151,516	$ 121,314