Consolidated Condensed Balance Sheets (Unaudited) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2014	Dec. 31, 2013
Current assets:
Cash and cash equivalents	$ 956	$ 13,650
Receivables:
Trade, net	75,176	70,869
Other	6,459	4,142
Prepaid expenses and other	13,949	15,274
Deferred income taxes	3,545	3,415
Total current assets	100,085	107,350
Property and equipment:
Accumulated depreciation	(174,627)	(164,916)
Net property and equipment	458,066	415,009
Other assets	3,991	3,443
TOTAL ASSETS	562,142	525,802
Current liabilities:
Accounts payable and accrued liabilities	42,063	38,624
Insurance and claims accruals	15,012	14,404
Total current liabilities	57,075	53,028
Long-term debt	16,757
Deferred income taxes	115,918	113,637
Total liabilities	189,750	166,665
Stockholders’ equity:
Preferred stock, $.01 par value per share; 2,000,000 shares authorized; no shares issued and outstanding	0	0
Common stock, $.01 par value per share; 48,000,000 shares authorized; 33,398,329 shares at June 30, 2014, and 33,301,048 shares at December 31, 2013, issued and outstanding	334	333
Additional paid-in capital	86,787	85,077
Retained earnings	285,271	273,727
Total stockholders’ equity	372,392	359,137
TOTAL LIABILITIES AND STOCKHOLDERS’ EQUITY	562,142	525,802
Office Equipment And Other [Member]
Property and equipment:
Revenue equipment, buildings and land, office equipment and other	$ 632,693	$ 579,925