Condensed Consolidated Balance Sheets (Current Period Unaudited) - USD ($) $ in Thousands	Mar. 31, 2017	Dec. 31, 2016
Current assets:
Cash and cash equivalents	$ 12,261	$ 6,377
Trade accounts receivable, net	707,433	745,288
Prepaid expenses and other	173,647	194,016
Total current assets	893,341	945,681
Property and equipment, at cost	4,331,100	4,258,915
Less accumulated depreciation	1,500,472	1,440,124
Net property and equipment	2,830,628	2,818,791
Other assets	46,426	64,516
Total assets	3,770,395	3,828,988
Current liabilities:
Trade accounts payable	369,763	384,308
Claims accruals	106,835	109,745
Accrued payroll	57,083	51,929
Other accrued expenses	52,844	27,152
Total current liabilities	586,525	573,134
Long-term debt	950,558	986,278
Other long-term liabilities	68,457	64,881
Deferred income taxes	792,561	790,634
Stockholders' equity	1,372,294	1,414,061
Total liabilities and stockholders' equity	$ 3,770,395	$ 3,828,988