Income Taxes	6 Months Ended
Jun. 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. The Company continues to analyze the impact of the Tax Act and expects 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 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 EAETR (estimated annual effective tax rate) and have not provided additional GILTI on deferred items. Deferred Tax Assets Net deferred income tax assets at June 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. The Company’s total net deferred tax assets at June 30, 2018 were $15.8 million. In preparing the Company’s condensed consolidated financial statements, management assesses the likelihood that its deferred tax assets will be realized from future taxable income. In evaluating the Company’s ability to recover its deferred income tax assets, management considers all available positive and negative evidence, including its 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 its provisions for income taxes, its deferred tax assets and liabilities, and its future taxable income for purposes of assessing its ability to utilize any future tax benefit from its deferred tax assets. Although management believes that its 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 June 30, 2018, the Company continues to demonstrate three-year cumulative pre-tax income in the U.S. federal and Arizona tax jurisdictions; however, the Company's 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 the Company’s 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 the Company’s deferred tax assets will not be realized and has established a valuation allowance. The Company has 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 $3.8 million as of June 30, 2018. In addition, management accrued $0.1 million for estimated uncertain tax positions related to certain state income tax liabilities, for a total unrecognized tax benefit as of June 30, 2018 of $3.9 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 $3.9 million be recognized, the Company's effective tax rate would be favorably impacted. Approximately $2.1 million of the unrecognized tax benefit associated with R&D credits has been netted against the R&D deferred tax asset. Effective Tax Rate The Company’s overall effective tax rate for the six months ended June 30, 2018, after discrete period adjustments, was (7.9)%. Before discrete adjustments, the tax rate was 22.8%, 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, 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 a $6.1 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 six months ended June 30, 2018. Of this amount $3.4 million related to stock options exercised by the Company's CEO in connection with the Company's follow-on offering.

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. The Company continues to analyze the impact of the Tax Act and expects 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 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 EAETR (estimated annual effective tax rate) and have not provided additional GILTI on deferred items.

Deferred Tax Assets

Net deferred income tax assets at June 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. The Company’s total net deferred tax assets at June 30, 2018 were $15.8 million.

In preparing the Company’s condensed consolidated financial statements, management assesses the likelihood that its deferred tax assets will be realized from future taxable income. In evaluating the Company’s ability to recover its deferred income tax assets, management considers all available positive and negative evidence, including its 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 its provisions for income taxes, its deferred tax assets and liabilities, and its future taxable income for purposes of assessing its ability to utilize any future tax benefit from its deferred tax assets.

Although management believes that its 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 June 30, 2018, the Company continues to demonstrate three-year cumulative pre-tax income in the U.S. federal and Arizona tax jurisdictions; however, the Company's 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 the Company’s 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 the Company’s deferred tax assets will not be realized and has established a valuation allowance.

The Company has 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 $3.8 million as of June 30, 2018. In addition, management accrued $0.1 million for estimated uncertain tax positions related to certain state income tax liabilities, for a total unrecognized tax benefit as of June 30, 2018 of $3.9 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 $3.9 million be recognized, the Company's effective tax rate would be favorably impacted. Approximately $2.1 million of the unrecognized tax benefit associated with R&D credits has been netted against the R&D deferred tax asset.

Effective Tax Rate

The Company’s overall effective tax rate for the six months ended June 30, 2018, after discrete period adjustments, was (7.9)%. Before discrete adjustments, the tax rate was 22.8%, 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, 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 a $6.1 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 six months ended June 30, 2018. Of this amount $3.4 million related to stock options exercised by the Company's CEO in connection with the Company's follow-on offering.