Consolidated Condensed Balance Sheets - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Current assets:
Cash and cash equivalents	$ 83,130	$ 29,334
Accounts receivable, trade, less allowance of $8,897 and $8,686, respectively	347,902	341,104
Other receivables	44,363	23,491
Inventories and supplies	11,919	12,062
Prepaid taxes, licenses and permits	12,876	17,231
Other current assets	32,719	33,694
Total current assets	532,909	456,916
Property and equipment	2,410,791	2,405,335
Less – accumulated depreciation	873,449	862,077
Property and equipment, net	1,537,342	1,543,258
Other non-current assets	159,275	156,502
Total assets	2,229,526	2,156,676
Current liabilities:
Accounts payable	113,064	83,263
Current portion of long-term debt	0	25,000
Insurance and claims accruals	91,097	76,917
Accrued payroll	41,912	35,594
Accrued expenses	25,350	25,032
Income taxes payable	19,226	7,824
Other current liabilities	17,112	20,384
Total current liabilities	307,761	274,014
Long-term debt, net of current portion	175,000	175,000
Other long-term liabilities	41,485	43,114
Insurance and claims accruals, net of current portion	235,850	231,638
Deferred income taxes	241,700	237,870
Commitments and contingencies
Stockholders’ equity:
Common stock, $0.01 par value, 200,000,000 shares authorized; 80,533,536 shares issued; 67,918,148 and 67,931,726 shares outstanding, respectively	805	805
Paid-in capital	114,588	116,039
Retained earnings	1,478,616	1,438,916
Accumulated other comprehensive loss	(23,098)	(22,833)
Treasury stock, at cost; 12,615,388 and 12,601,810 shares, respectively	(343,181)	(337,887)
Total stockholders’ equity	1,227,730	1,195,040
Total liabilities and stockholders’ equity	$ 2,229,526	$ 2,156,676