Consolidated Condensed Balance Sheets (USD $) In Thousands, unless otherwise specified	Mar. 31, 2012	Dec. 31, 2011
Current assets:
Cash and cash equivalents	$ 12,072	$ 12,412
Accounts receivable, trade, less allowance of $10,243 and $10,154, respectively	213,201	218,712
Other receivables	9,374	9,213
Inventories and supplies	27,983	30,212
Prepaid taxes, licenses and permits	11,171	15,094
Current deferred income taxes	25,514	25,805
Other current assets	18,878	29,883
Total current assets	318,193	341,331
Property and equipment	1,673,961	1,625,008
Less - accumulated depreciation	689,686	682,872
Property and equipment, net	984,275	942,136
Other non-current assets	21,955	18,949
Total assets	1,324,423	1,302,416
Current liabilities:
Checks issued in excess of cash balances	7,407	6,671
Accounts payable	87,914	93,486
Insurance and claims accruals	59,512	62,681
Accrued payroll	22,676	19,483
Other current liabilities	24,286	16,504
Total current liabilities	201,795	198,825
Other long-term liabilities	14,901	14,194
Insurance and claims accruals, net of current portion	122,750	121,250
Deferred income taxes	239,736	243,000
Commitments and contingencies
Stockholders' equity:
Common stock, $0.01 par value, 200,000,000 shares authorized; 80,533,536 shares issued; 72,857,376 and 72,847,576 shares outstanding, respectively	805	805
Paid-in capital	95,524	94,396
Retained earnings	797,596	779,994
Accumulated other comprehensive loss	(3,985)	(5,170)
Treasury stock, at cost; 7,676,160 and 7,685,960 shares, respectively	(144,699)	(144,878)
Total stockholders' equity	745,241	725,147
Total liabilities and stockholders' equity	$ 1,324,423	$ 1,302,416