Condensed Consolidated Balance Sheets (Current Period Unaudited) - USD ($) $ in Thousands	Jun. 30, 2017	Dec. 31, 2016
Current assets:
Cash and cash equivalents	$ 7,274	$ 6,377
Trade accounts receivable, net	749,042	745,288
Prepaid expenses and other	152,035	194,016
Total current assets	908,351	945,681
Property and equipment, at cost	4,384,981	4,258,915
Less accumulated depreciation	1,564,951	1,440,124
Net property and equipment	2,820,030	2,818,791
Other assets	50,001	64,516
Total assets	3,778,382	3,828,988
Current liabilities:
Trade accounts payable	419,306	384,308
Claims accruals	114,073	109,745
Accrued payroll	46,288	51,929
Other accrued expenses	28,425	27,152
Total current liabilities	608,092	573,134
Long-term debt	943,174	986,278
Other long-term liabilities	66,118	64,881
Deferred income taxes	753,277	790,634
Stockholders' equity	1,407,721	1,414,061
Total liabilities and stockholders' equity	$ 3,778,382	$ 3,828,988