Consolidated Condensed Balance Sheets - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Current assets:
Cash and cash equivalents	$ 9,924	$ 13,626
Accounts receivable, trade, less allowance of $8,548 and $8,250, respectively	333,134	304,174
Other receivables	19,784	26,491
Inventories and supplies	11,596	11,694
Prepaid taxes, licenses and permits	7,698	15,972
Other current assets	31,831	28,272
Total current assets	413,967	400,229
Property and equipment	2,187,896	2,114,337
Less – accumulated depreciation	773,280	767,474
Property and equipment, net	1,414,616	1,346,863
Other non-current assets	142,671	60,899
Total assets	1,971,254	1,807,991
Current liabilities:
Checks issued in excess of cash balances	13,697	21,539
Accounts payable	91,916	73,802
Insurance and claims accruals	64,978	79,674
Accrued payroll	35,995	32,520
Other current liabilities	21,631	24,642
Total current liabilities	228,217	232,177
Long-term debt, net of current portion	95,000	75,000
Other long-term liabilities	11,945	12,575
Insurance and claims accruals, net of current portion	202,039	108,270
Deferred income taxes	212,492	195,187
Commitments and contingencies
Stockholders’ equity:
Common stock, $0.01 par value, 200,000,000 shares authorized; 80,533,536 shares issued; 71,831,485 and 72,409,222 shares outstanding, respectively	805	805
Paid-in capital	104,799	102,563
Retained earnings	1,324,416	1,267,871
Accumulated other comprehensive loss	(15,675)	(15,835)
Treasury stock, at cost; 8,702,051 and 8,124,314 shares, respectively	(192,784)	(170,622)
Total stockholders’ equity	1,221,561	1,184,782
Total liabilities and stockholders’ equity	$ 1,971,254	$ 1,807,991