Consolidated Condensed Balance Sheets (USD $) In Thousands, unless otherwise specified	Jun. 30, 2012	Dec. 31, 2011
Current assets:
Cash and cash equivalents	$ 18,184	$ 12,412
Accounts receivable, trade, less allowance of $10,457 and $10,154, respectively	219,635	218,712
Other receivables	9,693	9,213
Inventories and supplies	26,070	30,212
Prepaid taxes, licenses and permits	7,037	15,094
Current deferred income taxes	26,901	25,805
Other current assets	15,907	29,883
Total current assets	323,427	341,331
Property and equipment	1,666,943	1,625,008
Less – accumulated depreciation	686,737	682,872
Property and equipment, net	980,206	942,136
Other non-current assets	21,927	18,949
Total assets	1,325,560	1,302,416
Current liabilities:
Checks issued in excess of cash balances	0	6,671
Accounts payable	77,153	93,486
Insurance and claims accruals	55,274	62,681
Accrued payroll	23,328	19,483
Other current liabilities	23,017	16,504
Total current liabilities	178,772	198,825
Other long-term liabilities	15,074	14,194
Insurance and claims accruals, net of current portion	120,950	121,250
Deferred income taxes	237,978	243,000
Stockholders' equity:
Common stock, $0.01 par value, 200,000,000 shares authorized; 80,533,536 shares issued; 72,869,626 and 72,847,576 shares outstanding, respectively	805	805
Paid-in capital	96,628	94,396
Retained earnings	824,633	779,994
Accumulated other comprehensive loss	(4,804)	(5,170)
Treasury stock, at cost; 7,663,910 and 7,685,960 shares, respectively	(144,476)	(144,878)
Total stockholders' equity	772,786	725,147
Total liabilities and stockholders' equity	$ 1,325,560	$ 1,302,416