Income taxes	6 Months Ended
Jun. 30, 2018
Income Tax Disclosure [Abstract]
Income taxes	Income taxes We account for income taxes under the asset and liability method. Deferred tax assets and liabilities are recognized for the expected tax consequences of temporary differences between the tax bases of assets and liabilities and their reported amounts. Valuation allowances are established when necessary to reduce deferred tax assets to amounts which are more likely than not to be realized. We had a valuation allowance of $78 million at June 30, 2018 and December 31, 2017. A majority of the valuation allowance is related to the deferred tax assets of National Instruments Hungary Kft. (“NI Hungary”). We account for uncertainty in income taxes recognized in our financial statements using prescribed recognition thresholds and measurement attributes for financial statement disclosure of tax positions taken or expected to be taken on our tax returns. We had $10.9 million and $10.2 million of unrecognized tax benefits at June 30, 2018 and December 31, 2017, respectively, all of which would affect our effective income tax rate if recognized. We recorded a gross increase in unrecognized tax benefits of $0.3 million and $0.6 million for the three and six months ended June 30, 2018, respectively, as a result of the tax positions taken during these periods. As of June 30, 2018, it is reasonably possible that we will recognize tax benefits in the amount of $1.8 million in the next twelve months due to the closing of open tax years. The nature of the uncertainty is related to deductions taken on returns that have not been examined by the applicable tax authority. Our continuing policy is to recognize interest and penalties related to income tax matters in income tax expense. As of June 30, 2018, we had approximately $1.1 million accrued for interest related to uncertain tax positions. The tax years 2009 through 2018 remain open to examination by the major taxing jurisdictions to which we are subject. Our provision for income taxes reflected an effective tax rate of 11% and 14% for the three months ended June 30, 2018 and 2017, respectively, and 14% and 18% for the six months ended June 30, 2018 and 2017, respectively. For the three and six months ended June 30, 2018, our effective tax rate was lower than the U.S. federal statutory rate of 21% as a result of an enhanced deduction for certain research and development expenses, profits in foreign jurisdictions with reduced income tax rates, the research and development tax credit, a tax benefit from disqualifying dispositions of equity awards that do not ordinarily result in a tax benefit, excess tax benefits from share-based compensation, and the deduction for foreign-derived deduction eligible income, offset by the U.S. tax on global intangible low-taxed income. For the three and six months ended June 30, 2017, our effective tax rate was lower than the U.S. federal statutory rate of 35% as a result of an enhanced deduction for certain research and development expenses, profits in foreign jurisdictions with reduced income tax rates, the research and development tax credit, and a tax benefit from disqualifying dispositions of equity awards that do not ordinarily result in a tax benefit, and excess tax benefits from share-based compensation. Our earnings in Hungary are subject to a statutory tax rate of 9%. In addition, our research and development activities in Hungary benefit from a tax law in Hungary that provides for an enhanced deduction for qualified research and development expenses. The tax position of our Hungarian operations resulted in income tax benefits of $2.9 million and $4.4 million for the three months ended June 30, 2018 and 2017, respectively, and $4.6 million and $7.3 million for the six months ended June 30, 2018 and 2017, respectively. Earnings from our operations in Malaysia are free of tax under a tax holiday effective January 1, 2013. This tax holiday expires in 2027. If we fail to satisfy the conditions of the tax holiday, this tax benefit may be terminated early. The income tax benefits of the tax holiday for the three and six months ended June 30, 2018 were approximately $0.5 million and $1.1 million, respectively. The impact of the tax holiday on a per share basis for each of the three and six months ended June 30, 2018 was a benefit of $0.01 per share. The income tax benefits of the tax holiday for the three and six months ended June 30, 2017 were approximately $0.6 million and $1.1 million, respectively. The impact of the tax holiday on a per share basis for each of the three and six months ended June 30, 2017 was a benefit of $0.01 per share. No other taxing jurisdictions had a significant impact on our effective tax rate. We have not entered into any advanced pricing or other agreements with the IRS with regard to any foreign jurisdictions. The Tax Cuts and Jobs Act was enacted on December 22, 2017. The Act reduced the federal corporate tax rate from 35% to 21%, requires companies to pay a one-time transition tax on earnings of certain foreign subsidiaries that were previously tax deferred, and creates new taxes on certain foreign earnings. We are applying the guidance in SAB 118 when accounting for the enactment-date effects of the Act. As of June 30, 2018, we had not completed our accounting for the tax effects of enactment of the Act. However, we have made a reasonable estimate of the effects on our existing deferred tax balances and the one-time transition tax. At December 31, 2017, we recognized a provisional amount of $69.9 million, which is included as a component of income tax expense from continuing operations. We will continue to make and refine our calculations as additional analysis is completed. Our estimates may also be affected as we gain a more thorough understanding of the Act. During the six month period ended June 30, 2018, we did not recognize any adjustments to the provisional amounts recorded at December 31, 2017. The Act subjects a U.S. shareholder to tax on global intangible low-taxed income ("GILTI") earned by certain foreign subsidiaries. The FASB staff Q&A, Topic 740, No. 5, Accounting for Global Intangible Low-Taxed Income, states that an entity can make an accounting policy election to either recognize deferred taxes for temporary basis differences expected to reverse as GILTI in future years or provide for the tax expense related to GILTI in the years the tax is incurred as a period expense only. Given the complexity of the GILTI provisions, we are still evaluating the effects of the GILTI provisions and have not yet determined our accounting policy. At June 30, 2018, because we are still evaluating the GILTI provisions and our analysis of future taxable income that is subject to GILTI we have included GILTI related to current-year operations only in our estimated annual effective tax rate and have not provided additional GILTI on deferred items.

Income taxes

We account for income taxes under the asset and liability method. Deferred tax assets and liabilities are recognized for the expected tax consequences of temporary differences between the tax bases of assets and liabilities and their reported amounts. Valuation allowances are established when necessary to reduce deferred tax assets to amounts which are more likely than not to be realized. We had a valuation allowance of $78 million at June 30, 2018 and December 31, 2017. A majority of the valuation allowance is related to the deferred tax assets of National Instruments Hungary Kft. (“NI Hungary”).

We account for uncertainty in income taxes recognized in our financial statements using prescribed recognition thresholds and measurement attributes for financial statement disclosure of tax positions taken or expected to be taken on our tax returns. We had $10.9 million and $10.2 million of unrecognized tax benefits at June 30, 2018 and December 31, 2017, respectively, all of which would affect our effective income tax rate if recognized. We recorded a gross increase in unrecognized tax benefits of $0.3 million and $0.6 million for the three and six months ended June 30, 2018, respectively, as a result of the tax positions taken during these periods. As of June 30, 2018, it is reasonably possible that we will recognize tax benefits in the amount of $1.8 million in the next twelve months due to the closing of open tax years. The nature of the uncertainty is related to deductions taken on returns that have not been examined by the applicable tax authority. Our continuing policy is to recognize interest and penalties related to income tax matters in income tax expense. As of June 30, 2018, we had approximately $1.1 million accrued for interest related to uncertain tax positions. The tax years 2009 through 2018 remain open to examination by the major taxing jurisdictions to which we are subject.

Our provision for income taxes reflected an effective tax rate of 11% and 14% for the three months ended June 30, 2018 and 2017, respectively, and 14% and 18% for the six months ended June 30, 2018 and 2017, respectively. For the three and six months ended June 30, 2018, our effective tax rate was lower than the U.S. federal statutory rate of 21% as a result of an enhanced deduction for certain research and development expenses, profits in foreign jurisdictions with reduced income tax rates, the research and development tax credit, a tax benefit from disqualifying dispositions of equity awards that do not ordinarily result in a tax benefit, excess tax benefits from share-based compensation, and the deduction for foreign-derived deduction eligible income, offset by the U.S. tax on global intangible low-taxed income.

For the three and six months ended June 30, 2017, our effective tax rate was lower than the U.S. federal statutory rate of 35% as a result of an enhanced deduction for certain research and development expenses, profits in foreign jurisdictions with reduced income tax rates, the research and development tax credit, and a tax benefit from disqualifying dispositions of equity awards that do not ordinarily result in a tax benefit, and excess tax benefits from share-based compensation.

Our earnings in Hungary are subject to a statutory tax rate of 9%. In addition, our research and development activities in Hungary benefit from a tax law in Hungary that provides for an enhanced deduction for qualified research and development expenses. The tax position of our Hungarian operations resulted in income tax benefits of $2.9 million and $4.4 million for the three months ended June 30, 2018 and 2017, respectively, and $4.6 million and $7.3 million for the six months ended June 30, 2018 and 2017, respectively.

Earnings from our operations in Malaysia are free of tax under a tax holiday effective January 1, 2013. This tax holiday expires in 2027. If we fail to satisfy the conditions of the tax holiday, this tax benefit may be terminated early. The income tax benefits of the tax holiday for the three and six months ended June 30, 2018 were approximately $0.5 million and $1.1 million, respectively. The impact of the tax holiday on a per share basis for each of the three and six months ended June 30, 2018 was a benefit of $0.01 per share. The income tax benefits of the tax holiday for the three and six months ended June 30, 2017 were approximately $0.6 million and $1.1 million, respectively. The impact of the tax holiday on a per share basis for each of the three and six months ended June 30, 2017 was a benefit of $0.01 per share.

No other taxing jurisdictions had a significant impact on our effective tax rate. We have not entered into any advanced pricing or other agreements with the IRS with regard to any foreign jurisdictions.

The Tax Cuts and Jobs Act was enacted on December 22, 2017. The Act reduced the federal corporate tax rate from 35% to 21%, requires companies to pay a one-time transition tax on earnings of certain foreign subsidiaries that were previously tax deferred, and creates new taxes on certain foreign earnings.

We are applying the guidance in SAB 118 when accounting for the enactment-date effects of the Act. As of June 30, 2018, we had not completed our accounting for the tax effects of enactment of the Act. However, we have made a reasonable estimate of the effects on our existing deferred tax balances and the one-time transition tax. At December 31, 2017, we recognized a provisional amount of $69.9 million, which is included as a component of income tax expense from continuing operations. We will continue to make and refine our calculations as additional analysis is completed. Our estimates may also be affected as we gain a more thorough understanding of the Act. During the six month period ended June 30, 2018, we did not recognize any adjustments to the provisional amounts recorded at December 31, 2017.

The Act subjects a U.S. shareholder to tax on global intangible low-taxed income ("GILTI") earned by certain foreign subsidiaries. The FASB staff Q&A, Topic 740, No. 5, Accounting for Global Intangible Low-Taxed Income, states that an entity can make an accounting policy election to either recognize deferred taxes for temporary basis differences expected to reverse as GILTI in future years or provide for the tax expense related to GILTI in the years the tax is incurred as a period expense only. Given the complexity of the GILTI provisions, we are still evaluating the effects of the GILTI provisions and have not yet determined our accounting policy. At June 30, 2018, because we are still evaluating the GILTI provisions and our analysis of future taxable income that is subject to GILTI we have included GILTI related to current-year operations only in our estimated annual effective tax rate and have not provided additional GILTI on deferred items.