9.	Income Taxes

On an interim basis, we estimate that the anticipated annual effective tax rate for the provision for income taxes and record a quarterly income tax provision in accordance with this anticipated annual rate. The effective tax rate may be subject to fluctuations during the year as new information is obtained, which may affect the assumptions used to estimate the annual effective tax rate, including factors such as the valuation allowances against deferred tax assets, the recognition or derecognition of tax benefits related to uncertain tax positions, expected utilization of R&D tax credits and changes in or the interpretation of tax laws in jurisdictions where the we conduct business. The American Taxpayer Relief Act of 2012 was enacted on January 2, 2013 and retroactively reinstated the U.S. R&D tax credit to January 1, 2012. During the six months ended June 30, 2013 we recognized $0.4 million as a discrete tax benefit due to the retroactive reinstatement of the U.S. R&D tax credit for 2012.

Our provision for income taxes is computed using the asset and liability method, under which deferred tax assets and liabilities are recognized for the expected future tax consequences of temporary differences between the financial reporting and tax bases of assets and liabilities, and for the expected future tax benefit to be derived from tax loss and credit carryforwards. Deferred tax assets and liabilities are determined using the enacted tax rates in effect for the years in which those tax assets are expected to be realized. A valuation allowance is established when it is more likely than not the future realization of all or some of the deferred tax assets will not be achieved. The evaluation of the need for a valuation allowance is performed on a jurisdiction by jurisdiction basis, and includes a review of all available positive and negative evidence.

Based on the weight of both positive and negative evidence, we concluded that it is more likely than not that the domestic net deferred tax assets would be realized, and therefore, we released our domestic valuation allowance during the quarter ended March 31, 2012. We released approximately $23 million as part of the projected annual effective tax rate and released the remaining $24 million of the domestic valuation allowance as a discrete item in the quarter ended March 31, 2012. We maintain a valuation allowance against our foreign net deferred tax assets as we continue to conclude it not more likely than not that the foreign net deferred tax assets will be realized.

We recognize excess tax benefits associated with share-based compensation to stockholders’ equity only when realized. When assessing whether excess tax benefits relating to share-based compensation have been realized, we follow the with-and-without approach, excluding any indirect effects of the excess tax deductions. Under this approach, excess tax benefits related to share-based compensation are not deemed to be realized until after the utilization of all other tax benefits available to us.

We recognize the impact of a tax position in our financial statements only if that position is more likely than not of being sustained upon examination by taxing authorities, based on the technical merits of the position. Any interest and penalties related to uncertain tax positions will be reflected in income tax expense.