Condensed Consolidated Balance Sheets (Current Period Unaudited) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Current assets:
Cash and cash equivalents	$ 570,918	$ 313,302
Trade accounts receivable, net	1,293,924	1,124,403
Prepaid expenses and other	344,457	404,412
Total current assets	2,209,299	1,842,117
Property and equipment, at cost	6,108,195	5,908,710
Less accumulated depreciation	2,390,467	2,219,816
Net property and equipment	3,717,728	3,688,894
Goodwill and intangible assets, net	204,886	212,122
Other assets	191,481	185,215
Total assets	6,323,394	5,928,348
Current liabilities:
Trade accounts payable	674,856	587,510
Claims accruals	282,331	276,056
Accrued payroll	174,718	130,943
Other accrued expenses	96,450	90,294
Total current liabilities	1,228,355	1,084,803
Long-term debt	1,303,467	1,305,424
Other long-term liabilities	263,576	245,961
Deferred income taxes	728,968	692,022
Stockholders' equity	2,799,028	2,600,138
Total liabilities and stockholders' equity	$ 6,323,394	$ 5,928,348