Note 5 - Income Taxes	6 Months Ended
Dec. 31, 2015
Notes to Financial Statements
Income Tax Disclosure [Text Block]	5 . Income Taxes During the three months ended December 31, 2015 and 2014, our effective tax rates were 35.8% and 37.2%, respectively. During the six months ended December 31, 2015 and 2014, our effective tax rates were 36.3% and 36.1%, respectively. In determining our quarterly provision for income taxes, we use an estimated annual effective tax rate, which is based on our expected annual income, statutory tax rates, nontaxable and nondeductible items of income and expense, and the ultimate outcome of tax audits. The change in the proportion of income from domestic and foreign sources affects our effective tax rate. Income tax expense also varies from the amount computed by applying the statutory federal tax rate to income before income taxes primarily due to state income taxes, net of federal income tax effect, adjusted for permanent differences, the most significant of which is the effect of the per diem pay structure for drivers. Under this pay structure, drivers who meet the requirements and elect to receive per diem pay are generally required to receive non-taxable per diem pay in lieu of a portion of their taxable wages. This per diem program increases our drivers’ net pay per mile, after taxes, while decreasing gross pay, before taxes. As a result, salaries, wages, and employee benefits are slightly lower, and our effective income tax rate is higher than the statutory rate. Generally, as pre-tax income increases, the impact of the driver per diem program on our effective tax rate decreases because aggregate per diem pay becomes smaller in relation to pre-tax income. Due to the partially nondeductible effect of per diem pay, our tax rate will fluctuate in future periods based on fluctuations in earnings and in the number of drivers who elect to be paid under this pay structure. We follow ASC Topic 740-10-25 in accounting for uncertainty in income taxes ("Topic 740"). Topic 740 prescribes a recognition threshold and measurement attribute for the financial statement recognition and measurement of a tax position taken or expected to be taken in a tax return. We account for any uncertainty in income taxes by determining whether it is more likely than not that a tax position taken or expected to be taken in a tax return will be sustained upon examination by the appropriate taxing authority based on the technical merits of the position. In that regard, we have analyzed filing positions in our federal and applicable state tax returns for all open tax years. The only periods subject to examination for our federal returns are the 2012 through 2014 tax years. We believe that our income tax filing positions and deductions will be sustained on audit and do not anticipate any adjustments that will result in a material change to our consolidated financial position, results of operations, or cash flows. As of December 31, 2015, we recorded a $0.5 million liability for unrecognized tax benefits, a portion of which represents penalties and interest.

Income Taxes

During the three months ended December 31, 2015 and 2014, our effective tax rates were 35.8% and 37.2%, respectively. During the six months ended December 31, 2015 and 2014, our effective tax rates were 36.3% and 36.1%, respectively. In determining our quarterly provision for income taxes, we use an estimated annual effective tax rate, which is based on our expected annual income, statutory tax rates, nontaxable and nondeductible items of income and expense, and the ultimate outcome of tax audits. The change in the proportion of income from domestic and foreign sources affects our effective tax rate. Income tax expense also varies from the amount computed by applying the statutory federal tax rate to income before income taxes primarily due to state income taxes, net of federal income tax effect, adjusted for permanent differences, the most significant of which is the effect of the per diem pay structure for drivers. Under this pay structure, drivers who meet the requirements and elect to receive per diem pay are generally required to receive non-taxable per diem pay in lieu of a portion of their taxable wages. This per diem program increases our drivers’ net pay per mile, after taxes, while decreasing gross pay, before taxes. As a result, salaries, wages, and employee benefits are slightly lower, and our effective income tax rate is higher than the statutory rate. Generally, as pre-tax income increases, the impact of the driver per diem program on our effective tax rate decreases because aggregate per diem pay becomes smaller in relation to pre-tax income. Due to the partially nondeductible effect of per diem pay, our tax rate will fluctuate in future periods based on fluctuations in earnings and in the number of drivers who elect to be paid under this pay structure.

We follow ASC Topic 740-10-25 in accounting for uncertainty in income taxes ("Topic 740"). Topic 740 prescribes a recognition threshold and measurement attribute for the financial statement recognition and measurement of a tax position taken or expected to be taken in a tax return. We account for any uncertainty in income taxes by determining whether it is more likely than not that a tax position taken or expected to be taken in a tax return will be sustained upon examination by the appropriate taxing authority based on the technical merits of the position. In that regard, we have analyzed filing positions in our federal and applicable state tax returns for all open tax years. The only periods subject to examination for our federal returns are the 2012 through 2014 tax years. We believe that our income tax filing positions and deductions will be sustained on audit and do not anticipate any adjustments that will result in a material change to our consolidated financial position, results of operations, or cash flows. As of December 31, 2015, we recorded a $0.5 million liability for unrecognized tax benefits, a portion of which represents penalties and interest.