Consolidated Condensed Balance Sheets (USD $) In Thousands, unless otherwise specified	Sep. 30, 2014	Dec. 31, 2013
Current assets:
Cash and cash equivalents	$ 47,598	$ 23,678
Accounts receivable, trade, less allowance of $10,307 and $9,939, respectively	264,406	231,647
Other receivables	22,244	10,769
Inventories and supplies	15,167	15,743
Prepaid taxes, licenses and permits	6,503	15,064
Current deferred income taxes	26,668	25,315
Other current assets	31,522	27,445
Total current assets	414,108	349,661
Property and equipment	1,764,972	1,727,737
Less – accumulated depreciation	771,188	750,219
Property and equipment, net	993,784	977,518
Other non-current assets	41,489	26,918
Total assets	1,449,381	1,354,097
Current liabilities:
Accounts payable	89,073	66,678
Insurance and claims accruals	65,070	59,811
Accrued payroll	32,256	22,785
Other current liabilities	20,388	18,457
Total current liabilities	206,787	167,731
Long-term debt, net of current portion	75,000	40,000
Other long-term liabilities	19,667	14,710
Insurance and claims accruals, net of current portion	130,825	131,900
Deferred income taxes	212,632	227,237
Commitments and contingencies
Stockholders’ equity:
Common stock, $0.01 par value, 200,000,000 shares authorized; 80,533,536 shares issued; 71,756,576 and 72,713,920 shares outstanding, respecitvely	805	805
Paid-in capital	102,792	98,534
Retained earnings	885,978	830,842
Accumulated other comprehensive loss	(5,947)	(4,631)
Treasury stock, at cost; 8,776,960 and 7,819,616 shares, respectively	(179,158)	(153,031)
Total stockholders’ equity	804,470	772,519
Total liabilities and stockholders’ equity	$ 1,449,381	$ 1,354,097