Condensed Consolidated Balance Sheets (Current Period Unaudited) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Current assets:
Cash and cash equivalents	$ 7,587	$ 14,612
Trade accounts receivable, net	1,095,638	920,767
Prepaid expenses and other	239,257	403,349
Total current assets	1,342,482	1,338,728
Property and equipment, at cost	5,064,126	4,670,464
Less accumulated depreciation	1,822,619	1,687,133
Net property and equipment	3,241,507	2,983,331
Other assets, net	137,682	143,290
Total assets	4,721,671	4,465,349
Current liabilities:
Current portion of long-term debt	248,680
Trade accounts payable	569,453	598,594
Claims accruals	279,136	251,980
Accrued payroll	74,802	42,382
Other accrued expenses	40,589	28,888
Total current liabilities	1,212,660	921,844
Long-term debt	820,864	1,085,649
Other long-term liabilities	89,141	76,661
Deferred income taxes	518,428	541,870
Stockholders' equity	2,080,578	1,839,325
Total liabilities and stockholders' equity	$ 4,721,671	$ 4,465,349