Consolidated Condensed Balance Sheets (USD $) In Thousands	Jun. 30, 2011	Dec. 31, 2010
Current assets:
Cash and cash equivalents	$ 23,483	$ 13,966
Accounts receivable, trade, less allowance of $10,156 and $9,484, respectively	213,250	190,264
Other receivables	10,585	10,431
Inventories and supplies	24,973	16,868
Prepaid taxes, licenses and permits	7,298	14,934
Current deferred income taxes	29,084	27,829
Other current assets	26,204	23,407
Total current assets	334,877	297,699
Property and equipment	1,577,067	1,549,637
Less - accumulated depreciation	701,289	708,582
Property and equipment, net	875,778	841,055
Other non-current assets	12,480	12,798
Total assets	1,223,135	1,151,552
Current liabilities:
Accounts payable	66,046	57,708
Insurance and claims accruals	65,609	71,857
Accrued payroll	21,084	18,838
Other current liabilities	17,203	20,037
Total current liabilities	169,942	168,440
Other long-term liabilities	10,907	10,380
Insurance and claims accruals, net of current portion	117,750	113,250
Deferred income taxes	214,302	190,507
Commitments and contingencies
Stockholders' equity:
Common stock, $0.01 par value, 200,000,000 shares authorized; 80,533,536 shares issued; 72,805,115 and 72,644,998 shares outstanding, respectively	805	805
Paid-in capital	93,029	91,872
Retained earnings	764,748	728,216
Accumulated other comprehensive income (loss)	(2,696)	(3,420)
Treasury stock, at cost; 7,728,421 and 7,888,538 shares, respectively	(145,652)	(148,498)
Total stockholders' equity	710,234	668,975
Total liabilities and stockholders' equity	$ 1,223,135	$ 1,151,552