Income Taxes (Details 2) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Deferred tax assets:
Federal net operating loss carryforwards	$ 106,418	$ 158,638
State net operating loss carryforwards	96,811	104,752
Deferred Compensation	41,241	57,030
Foreign tax credits	37,390	32,958
Alternative minimum tax credits	6,591	6,591
Accrued insurance, pension liability and other	74,282	67,172
Total deferred tax asset	362,733	427,141
Less: Valuation allowance	88,398	97,284
Net deferred tax assets	274,335	329,857
Deferred tax liabilities:
Property and equipment	288,504	290,432
Intangible assets and other	126,104	124,209
Total deferred tax liabilities	414,608	414,641
Net deferred tax liability	140,273	$ 84,784
Unrealized Excess Tax Benefits, Gross	244,200
Estimated excess income tax benefits pertaining to share-based payments recognized as an increase in additional paid in capital at current income tax rates	95,700
U.S. federal
Details of net operating loss carryforwards
Net operating loss carryforwards	400,000
State
Details of net operating loss carryforwards
Net operating loss carryforwards	$ 3,800,000