Income Taxes (Details 2) (USD $)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
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	$ 32,983,000	$ (14,683,000)	$ 52,888,000
Purchase accounting (gain) adjustment		1,999,000	(5,455,000)
State income tax provision (benefit), net of Federal income tax benefit	2,220,000	(1,810,000)	3,485,000
Valuation allowance changes affecting the provision for income taxes	1,614,000
Other, net	(2,078,000)	(8,341,000)	(1,367,000)
Provision (benefit) for income taxes	34,739,000	(22,835,000)	49,551,000
Benefits determined in connection with the preparation of the Company's 2010 tax return		7,200,000
Deferred tax assets:
Intangible Asset	37,031,000	37,404,000
Accrued benefits	40,469,000	35,460,000
Net operating loss carryforward	118,448,000	128,134,000
AMT credit carryforward	15,882,000	15,882,000
Deferred aircraft credits	48,124,000	49,867,000
Accrued reserves and other	31,846,000	24,538,000
Total deferred tax assets	291,800,000	291,285,000
Valuation allowance	(1,614,000)
Deferred tax liabilities:
Accelerated depreciation	(823,487,000)	(789,641,000)
Total deferred tax liabilities	(823,487,000)	(789,641,000)
Net deferred tax liability	$ (533,301,000)	$ (498,356,000)