Quarterly report pursuant to Section 13 or 15(d)

Income Taxes

Income Taxes
6 Months Ended
Jun. 30, 2018
Income Tax Disclosure [Abstract]  
Income Taxes
Income Taxes
The effective income tax rate, which is the provision for income taxes as a percentage of income before provision for income taxes, was 26.4% and 29.2% for the six months ended June 30, 2018 and 2017, respectively. The decrease in the effective income tax rate for the six months ended June 30, 2018 is largely driven by the decreased federal tax rate. The effective income tax rates for the six months ended June 30, 2018 and 2017 also differed from the U.S. Federal statutory rate of 21% and 35%, respectively, due to state income taxes, stock compensation, utilization of tax credits, and the domestic manufacturing deduction in 2017.
On December 22, 2017, the Tax Act was signed into law. The Tax Act made broad and complex changes to the U.S. tax code which include: a lowering of the U.S. federal corporate income tax rate from 35% to 21% effective January 1, 2018, accelerated expensing of qualified capital investments for a specific period, and a transition from a worldwide to a territorial tax system which will require companies to pay a one-time transition tax on certain unrepatriated earnings from foreign subsidiaries that is payable over eight years.
The SEC staff issued Staff Accounting Bulletin No. 118 (“SAB 118”), which provides guidance on accounting for the tax effects of the Tax Act. SAB 118 allows a company to record a provisional amount when it does not have the necessary information available, prepared, or analyzed in reasonable detail to complete its accounting for the change in the tax law. The measurement period ends when a company has obtained, prepared and analyzed the information necessary to finalize its accounting, but cannot extend beyond one year.
Our accounting for the Tax Act is still ongoing. As noted at year-end, however, we were able to reasonably estimate certain effects and, therefore, recorded provisional adjustments associated with the transition tax, the re-measurement of deferred taxes, our reassessment of permanently reinvested earnings, excessive compensation, uncertain tax positions and valuation allowances. We have not made any additional measurement-period adjustments related to these items during the six months ended June 30, 2018. We continue to gather additional information related to the above items and we anticipate additional IRS guidance relative to the impacts of the Tax Act will be forthcoming throughout 2018.
As of both June 30, 2018 and December 31, 2017, we had $25.2 million of unrecognized tax benefits, of which $8.5 million would impact the effective tax rate, if recognized. Estimated interest and penalties related to the underpayment of income taxes are classified as a component of the provision for income taxes in the accompanying consolidated statements of operations. Accrued interest and penalties as of June 30, 2018 and December 31, 2017 were $2.5 million and $2.1 million, respectively. Our liability for uncertain tax positions, including accrued interest and penalties, of $27.7 million and $27.3 million at June 30, 2018 and December 31, 2017, respectively, are presented in other noncurrent liabilities in the accompanying consolidated balance sheets.
Our U.S. federal returns for the period ended December 31, 2014 and all subsequent periods remain open for audit. In addition, the majority of state returns for the period ended December 31, 2013 and all subsequent periods remain open for audit.