Condensed Consolidated Balance Sheets (Current Period Unaudited) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2014	Dec. 31, 2013
Current assets:
Cash and cash equivalents	$ 124,212	$ 5,831
Trade accounts receivable, net	635,111	568,519
Prepaid expenses and other	82,745	105,853
Total current assets	842,068	680,203
Property and equipment, at cost	3,399,270	3,259,814
Less accumulated depreciation	1,163,169	1,147,610
Net property and equipment	2,236,101	2,112,204
Other assets	37,556	26,997
Total assets	3,115,725	2,819,404
Current liabilities:
Current portion of long-term debt	100,000	250,000
Trade accounts payable	371,235	305,465
Claims accruals	77,047	68,221
Accrued payroll	65,801	72,063
Other accrued expenses	46,236	14,062
Deferred income taxes	2,485	2,485
Total current liabilities	662,804	712,296
Long-term debt	752,207	458,417
Other long-term liabilities	59,910	58,274
Deferred income taxes	572,679	577,965
Stockholders' equity	1,068,125	1,012,452
Total liabilities and stockholders' equity	$ 3,115,725	$ 2,819,404