Income Taxes Schedule of Deferred Tax Assets and Liabilities (Details) (USD $)	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Components of Deferred Tax Assets [Abstract]
Auction rate preferred securities	$ 1,239,000	$ 1,248,000
Intangibles	20,829,000	21,594,000
Employee benefits and insurance claims accruals	9,126,000	3,634,000
Accounts receivable reserve	369,000	42,000
Employee stock based compensation	6,914,000	6,099,000
Accrued expenses not deductible for tax purposes	1,149,000	0
Accrued revenue not income for book purposes	2,212,000	3,393,000
Federal and state net operating loss and AMT credit carryforward	39,310,000	21,568,000
Foreign net operating loss carryforward	6,782,000	5,713,000
Deferred Tax Assets, Gross	87,930,000	63,291,000
Valuation allowance	(1,239,000)	(1,248,000)
Total deferred tax assets	86,691,000	62,043,000
Components of Deferred Tax Liabilities [Abstract]
Accrued expenses not deductible for tax purposes	0	105,000
Property and equipment	165,268,000	132,231,000
Total deferred tax liabilities	165,268,000	132,336,000
Net deferred tax liabilities	(78,577,000)	(70,293,000)
Other than Temporary Impairment Losses, Investments, Portion Recognized in Earnings, Net	0	3,331,000	0
Undistributed Earnings of Foreign Subsidiaries	$ (16,700,000)