Income taxes	6 Months Ended
Jun. 30, 2013
Income taxes
Income taxes	8. Income taxes We calculate our interim income tax provision in accordance with ASC 270, Interim Reporting, and ASC 740, Accounting for Income Taxes. At the end of each interim period, we estimate the annual effective tax rate and apply that rate to our ordinary quarterly (loss) earnings. The tax expense or benefit related to significant, unusual, or extraordinary items is recognized in the interim period in which those items occur. In addition, the effect of changes in enacted tax laws, rates, or tax status is recognized in the interim period in which the change occurs. The computation of the annual estimated effective tax rate at each interim period requires certain estimates and significant judgment, including the expected operating income for the year, projections of the proportion of income earned and taxed in various states, permanent and temporary differences as a result of differences between amounts measured and recognized in accordance with tax laws and financial accounting standards, and the likelihood of recovering deferred tax assets generated in the current year. The accounting estimates used to compute the provision for income taxes may change as new events occur, additional information is obtained, or as the tax environment changes. During the six months ended June 30, 2013, we recognized excess windfall tax benefits of $3,758 from stock option exercises. These benefits will decrease income taxes payable for the year ended December 31, 2013, and were recorded as an increase to additional paid-in capital in the accompanying condensed consolidated balance sheet as of June 30, 2013. Income tax (benefit) expense of $(640) and $1,367 reflects an effective tax rate of 34.5% and 28.6% for the six months ended June 30, 2013 and 2012, respectively. Our effective tax rate differs from the statutory rate primarily due to benefits from disqualifying dispositions of incentive stock options for the six months ended June 30, 2013 and 2012 and non-tax deductible transaction costs related to the acquisition of Endeka for the six months ended June 30, 2013. Under current tax regulations, we do not receive a tax deduction for the issuance, exercise or disposition of incentive stock options if the employee meets certain holding requirements. If the employee does not meet the holding requirements, a disqualifying disposition occurs, at which time we may receive a tax deduction. We do not record tax benefits related to incentive stock options unless and until a disqualifying disposition is reported. At June 30, 2013, we have net deferred tax assets of $2,399, which includes net operating loss carry-forwards. As of June 30, 2013 and December 31, 2012, we had $392 of uncertain tax positions, $106 of which is a reduction to deferred tax assets, which is presented net of uncertain tax positions, in the accompanying condensed consolidated balance sheets. We are subject to taxation in the United States and in various states. Our tax years 2009 and forward are subject to examination by the IRS and our tax years 2007 and forward are subject to examination by material state jurisdictions. However, due to prior year loss carryovers, the IRS and state tax authorities may examine any tax years for which the carryovers are used to offset future taxable income.

Income taxes

6 Months Ended

Jun. 30, 2013

8. Income taxes

We calculate our interim income tax provision in accordance with ASC 270, Interim Reporting, and ASC 740, Accounting for Income Taxes. At the end of each interim period, we estimate the annual effective tax rate and apply that rate to our ordinary quarterly (loss) earnings. The tax expense or benefit related to significant, unusual, or extraordinary items is recognized in the interim period in which those items occur. In addition, the effect of changes in enacted tax laws, rates, or tax status is recognized in the interim period in which the change occurs.

The computation of the annual estimated effective tax rate at each interim period requires certain estimates and significant judgment, including the expected operating income for the year, projections of the proportion of income earned and taxed in various states, permanent and temporary differences as a result of differences between amounts measured and recognized in accordance with tax laws and financial accounting standards, and the likelihood of recovering deferred tax assets generated in the current year. The accounting estimates used to compute the provision for income taxes may change as new events occur, additional information is obtained, or as the tax environment changes.

During the six months ended June 30, 2013, we recognized excess windfall tax benefits of $3,758 from stock option exercises. These benefits will decrease income taxes payable for the year ended December 31, 2013, and were recorded as an increase to additional paid-in capital in the accompanying condensed consolidated balance sheet as of June 30, 2013.

Income tax (benefit) expense of $(640) and $1,367 reflects an effective tax rate of 34.5% and 28.6% for the six months ended June 30, 2013 and 2012, respectively. Our effective tax rate differs from the statutory rate primarily due to benefits from disqualifying dispositions of incentive stock options for the six months ended June 30, 2013 and 2012 and non-tax deductible transaction costs related to the acquisition of Endeka for the six months ended June 30, 2013. Under current tax regulations, we do not receive a tax deduction for the issuance, exercise or disposition of incentive stock options if the employee meets certain holding requirements. If the employee does not meet the holding requirements, a disqualifying disposition occurs, at which time we may receive a tax deduction. We do not record tax benefits related to incentive stock options unless and until a disqualifying disposition is reported. At June 30, 2013, we have net deferred tax assets of $2,399, which includes net operating loss carry-forwards. As of June 30, 2013 and December 31, 2012, we had $392 of uncertain tax positions, $106 of which is a reduction to deferred tax assets, which is presented net of uncertain tax positions, in the accompanying condensed consolidated balance sheets.

We are subject to taxation in the United States and in various states. Our tax years 2009 and forward are subject to examination by the IRS and our tax years 2007 and forward are subject to examination by material state jurisdictions. However, due to prior year loss carryovers, the IRS and state tax authorities may examine any tax years for which the carryovers are used to offset future taxable income.