Income Taxes (Details 2) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Income Taxes
Statutory Federal income tax rate (as a percent)	35.00%
Reconciliation between the statutory Federal income tax rate of 35% and the effective rate which is derived by dividing the provision (benefit) for income taxes by income (loss) before provision for income taxes
Computed ''expected'' provision (benefit) for income taxes at the statutory rates adjusted for permanent differences	$ 37,743	$ 32,983	$ (14,683)
Purchase accounting (gain) adjustment			1,999
State income tax provision (benefit), net of Federal income tax benefit	2,867	2,220	(1,810)
Valuation allowance changes affecting the provision for income taxes	1,430	1,614
Other, net	(2,464)	(2,078)	(8,341)
Provision (benefit) for income taxes	39,576	34,739	(22,835)
Deferred tax assets:
Intangible Asset	36,164	37,031
Accrued benefits	40,850	40,469
Net operating loss carryforward	85,885	118,448
AMT credit carryforward	17,649	15,882
Deferred aircraft credits	44,350	48,124
Accrued reserves and other	30,987	31,846
Total deferred tax assets	255,885	291,800
Valuation allowance	(3,044)	(1,614)
Deferred tax liabilities:
Accelerated depreciation	(824,149)	(823,487)
Total deferred tax liabilities	(824,149)	(823,487)
Net deferred tax liability	$ (571,308)	$ (533,301)