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Note 16 - Concentration of Risk and Enterprise Wide Disclosures (Tables)
12 Months Ended
Dec. 31, 2015
Notes Tables  
Schedule of Revenue by Major Customers by Reporting Segments [Table Text Block]
    Years Ended December 31,
    2015   2014   2013
    Amount   %   Amount   %   Amount   %
Texas Department of Transportation (“TXDOT”)   $ 84,129       13.5 %   $ *       * %   $ *       * %
California Department of Transportation (“Caltrans”)     96,470       15.5       97,637       14.5       92,159       16.6