Condensed Consolidated Balance Sheets (Current Period Unaudited) - USD ($) $ in Thousands	Sep. 30, 2016	Dec. 31, 2015
Current assets:
Cash and cash equivalents	$ 5,481	$ 5,566
Trade accounts receivable, net	775,020	654,542
Prepaid expenses and other	61,900	197,817
Total current assets	842,401	857,925
Property and equipment, at cost	4,209,080	4,019,451
Less accumulated depreciation	1,400,339	1,318,122
Net property and equipment	2,808,741	2,701,329
Other assets	78,852	70,290
Total assets	3,729,994	3,629,544
Current liabilities:
Trade accounts payable	402,913	340,332
Claims accruals	104,243	104,220
Accrued payroll	72,920	59,420
Other accrued expenses	20,769	28,445
Total current liabilities	600,845	532,417
Long-term debt	943,696	998,003
Other long-term liabilities	69,302	58,552
Deferred income taxes	731,068	740,220
Stockholders' equity	1,385,083	1,300,352
Total liabilities and stockholders' equity	$ 3,729,994	$ 3,629,544