Income Taxes (Details 2) (USD $)	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012
Deferred tax assets:
Federal net operating loss carryforwards	$ 241,712,000	$ 288,675,000
State net operating loss carryforwards	196,814,000	180,777,000
Foreign tax credits	17,387,000	0
Alternative minimum tax credits	6,591,000	6,591,000
Accrued insurance, pension liability and other	81,962,000	85,173,000
Total deferred tax asset	544,466,000	561,216,000
Less: Valuation allowance	190,288,000	177,353,000
Net deferred tax assets	354,178,000	383,863,000
Deferred tax liabilities:
Property and equipment	299,633,000	287,992,000
Intangible assets and other	128,614,000	123,455,000
Total deferred tax liabilities	428,247,000	411,447,000
Net deferred tax liability	74,069,000	27,584,000
Estimated income tax deductions related to share-based payments	144,300,000
Estimated excess income tax benefits pertaining to share-based payments recognized as an increase in additional paid in capital at current income tax rates	56,600,000
U.S. federal
Details of net operating loss carryforwards
Net operating loss carryforwards	800,000,000	900,000,000
State
Details of net operating loss carryforwards
Net operating loss carryforwards	$ 5,000,000,000	$ 4,700,000,000