Income Taxes	9 Months Ended
Sep. 30, 2018
Income Tax Disclosure [Abstract]
Income Taxes	Income Taxes ASC 740 requires a company to record the effects of a tax law change in the period of enactment; however, shortly after the enactment of the Tax Cuts and Jobs Act (the "Tax Act"), the SEC staff issued Staff Accounting Bulletin 118 ("SAB 118"), which 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 the company has obtained, prepared and analyzed the information necessary to finalize its accounting, but cannot extend beyond one year. We continue to analyze the impact of the Tax Act and expect that as additional guidance from IRS Treasury is provided, further updates will be necessary. The Tax Act imposes a U.S. entity 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 year 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 September 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 EAETR (estimated annual effective tax rate) and have not provided additional GILTI on deferred items. We file income tax returns for federal purposes and in many states, as well as in multiple foreign jurisdictions. Our tax filings remain subject to examination by applicable tax authorities for a certain length of time, generally three to four years, following the tax year to which these filings relate. Our U.S. federal income tax return for fiscal year 2016 is currently under audit by the Internal Revenue Service. Deferred Tax Assets Net deferred income tax assets at September 30, 2018, include capitalized R&D costs, R&D tax credits, stock-based compensation expense, deferred revenue, warranty and inventory reserves, accrued vacation, and other items, partially offset by accelerated depreciation expense and intangible amortization that is not tax deductible. Our total net deferred tax assets at September 30, 2018 were $18.1 million. In preparing our condensed consolidated financial statements, management assesses the likelihood that its deferred tax assets will be realized from future taxable income. In evaluating our ability to recover our deferred income tax assets, management considers all available positive and negative evidence, including our operating results, ongoing tax planning and forecasts of future taxable income on a jurisdiction by jurisdiction basis. A valuation allowance is established if it is determined that it is more likely than not that some portion or all of the net deferred tax assets will not be realized. Management exercises significant judgment in determining our provisions for income taxes, our deferred tax assets and liabilities, and our future taxable income for purposes of assessing our ability to utilize any future tax benefit from our deferred tax assets. Although management believes that our tax estimates are reasonable, the ultimate tax determination involves significant judgments that could become subject to audit by tax authorities in the ordinary course of business. As of each reporting date, management considers new evidence, both positive and negative, that could impact management’s view with regard to future realization of deferred tax assets. As of September 30, 2018, we continue to demonstrate three-year cumulative pre-tax income in the U.S. federal and Arizona tax jurisdictions; however, our Arizona R&D Tax Credits start to expire in 2018 with a significant tranche with a gross value of $1.2 million expiring if not used by the end of 2019. It appears that our long term investments, which impact short-term profits, will likely result in some of the R&D credits expiring before they are utilized. Therefore, management has concluded that it is more likely than not that a portion of our deferred tax assets will not be realized and has established a valuation allowance. We have claimed R&D tax credits of approximately $17.0 million for federal, Arizona and California income tax purposes related to tax years 2003 to 2018. Management has made the determination that it is more likely than not that the full benefit of the R&D tax credits will not be sustained upon examination and recorded a liability for unrecognized tax benefits of $3.6 million as of September 30, 2018. In addition, management accrued $0.2 million for estimated uncertain tax positions related to certain federal and state income tax liabilities, for a total liability for unrecognized tax benefit as of September 30, 2018 of $3.8 million. Management expects the amount of unrecognized tax benefit liability to increase by $0.2 million within the next 12 months. Should the unrecognized benefit of $3.8 million be recognized, our effective tax rate would be favorably impacted. Approximately $2.2 million of the unrecognized tax benefit associated with R&D credits has been netted against the R&D deferred tax asset. Effective Tax Rate Our overall effective tax rate for the nine months ended September 30, 2018, after discrete period adjustments, was (8.1)%. Before discrete adjustments, the tax rate was 24.0%, which is more than the federal statutory rate, primarily due to state taxes and non-deductible expenses for items such as meals and entertainment, executive compensation limitation under IRC section 162(m), lobbying fees, and an income inclusion from GILTI, offset by a reduction for foreign-derived intangible income ("FDII"). This was partially offset by R&D tax credit deductions. The effective tax rate was favorably impacted by an $8.1 million discrete tax benefit primarily associated with windfalls related to stock-based compensation for RSUs that vested or stock options that were exercised during the nine months ended September 30, 2018. Of this amount, $3.4 million related to stock options exercised by our CEO in connection with our follow-on offering, as discussed in Note 9.

Income Taxes

ASC 740 requires a company to record the effects of a tax law change in the period of enactment; however, shortly after the enactment of the Tax Cuts and Jobs Act (the "Tax Act"), the SEC staff issued Staff Accounting Bulletin 118 ("SAB 118"), which 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 the company has obtained, prepared and analyzed the information necessary to finalize its accounting, but cannot extend beyond one year. We continue to analyze the impact of the Tax Act and expect that as additional guidance from IRS Treasury is provided, further updates will be necessary.

The Tax Act imposes a U.S. entity 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 year 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 September 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 EAETR (estimated annual effective tax rate) and have not provided additional GILTI on deferred items.

We file income tax returns for federal purposes and in many states, as well as in multiple foreign jurisdictions. Our tax filings remain subject to examination by applicable tax authorities for a certain length of time, generally three to four years, following the tax year to which these filings relate. Our U.S. federal income tax return for fiscal year 2016 is currently under audit by the Internal Revenue Service.

Deferred Tax Assets

Net deferred income tax assets at September 30, 2018, include capitalized R&D costs, R&D tax credits, stock-based compensation expense, deferred revenue, warranty and inventory reserves, accrued vacation, and other items, partially offset by accelerated depreciation expense and intangible amortization that is not tax deductible. Our total net deferred tax assets at September 30, 2018 were $18.1 million.

In preparing our condensed consolidated financial statements, management assesses the likelihood that its deferred tax assets will be realized from future taxable income. In evaluating our ability to recover our deferred income tax assets, management considers all available positive and negative evidence, including our operating results, ongoing tax planning and forecasts of future taxable income on a jurisdiction by jurisdiction basis. A valuation allowance is established if it is determined that it is more likely than not that some portion or all of the net deferred tax assets will not be realized. Management exercises significant judgment in determining our provisions for income taxes, our deferred tax assets and liabilities, and our future taxable income for purposes of assessing our ability to utilize any future tax benefit from our deferred tax assets.

Although management believes that our tax estimates are reasonable, the ultimate tax determination involves significant judgments that could become subject to audit by tax authorities in the ordinary course of business. As of each reporting date, management considers new evidence, both positive and negative, that could impact management’s view with regard to future realization of deferred tax assets. As of September 30, 2018, we continue to demonstrate three-year cumulative pre-tax income in the U.S. federal and Arizona tax jurisdictions; however, our Arizona R&D Tax Credits start to expire in 2018 with a significant tranche with a gross value of $1.2 million expiring if not used by the end of 2019. It appears that our long term investments, which impact short-term profits, will likely result in some of the R&D credits expiring before they are utilized. Therefore, management has concluded that it is more likely than not that a portion of our deferred tax assets will not be realized and has established a valuation allowance.

We have claimed R&D tax credits of approximately $17.0 million for federal, Arizona and California income tax purposes related to tax years 2003 to 2018. Management has made the determination that it is more likely than not that the full benefit of the R&D tax credits will not be sustained upon examination and recorded a liability for unrecognized tax benefits of $3.6 million as of September 30, 2018. In addition, management accrued $0.2 million for estimated uncertain tax positions related to certain federal and state income tax liabilities, for a total liability for unrecognized tax benefit as of September 30, 2018 of $3.8 million. Management expects the amount of unrecognized tax benefit liability to increase by $0.2 million within the next 12 months. Should the unrecognized benefit of $3.8 million be recognized, our effective tax rate would be favorably impacted. Approximately $2.2 million of the unrecognized tax benefit associated with R&D credits has been netted against the R&D deferred tax asset.

Effective Tax Rate

Our overall effective tax rate for the nine months ended September 30, 2018, after discrete period adjustments, was (8.1)%. Before discrete adjustments, the tax rate was 24.0%, which is more than the federal statutory rate, primarily due to state taxes and non-deductible expenses for items such as meals and entertainment, executive compensation limitation under IRC section 162(m), lobbying fees, and an income inclusion from GILTI, offset by a reduction for foreign-derived intangible income ("FDII"). This was partially offset by R&D tax credit deductions. The effective tax rate was favorably impacted by an $8.1 million discrete tax benefit primarily associated with windfalls related to stock-based compensation for RSUs that vested or stock options that were exercised during the nine months ended September 30, 2018. Of this amount, $3.4 million related to stock options exercised by our CEO in connection with our follow-on offering, as discussed in Note 9.