Income Taxes	9 Months Ended
Oct. 28, 2018
Income Tax Disclosure [Abstract]
Income Taxes	Income Taxes We recognized an income tax benefit of $149 million and $3 million for the third quarter and first nine months of fiscal year 2019, respectively, and income tax expense of $58 million and $189 million for the third quarter and first nine months of fiscal year 2018, respectively. Income tax benefit as a percentage of income before income tax was 13.8% and nominal for the third quarter and first nine months of fiscal year 2019, respectively, and income tax expense as a percentage of income before tax was 6.5% and 8.9% for the third quarter and first nine months of fiscal year 2018, respectively. The decrease in our effective tax rate for the third quarter and first nine months of fiscal year 2019 as compared to the same periods in the prior fiscal year was primarily due to a decrease in the U.S. statutory tax rate from 35% to 21% as a result of U.S. tax reform, and a $138 million reduction in our provisional U.S. tax reform transition tax amount in the third quarter of fiscal year 2019, partially offset by a decrease in the impact of tax benefits from stock-based compensation. Our effective tax rates for the first nine months of fiscal years 2019 and 2018 were nominal and 8.9%, respectively, and were lower than the U.S. federal statutory rates of 21% and 33.9%, for fiscal years 2019 and 2018, respectively, due to income earned in jurisdictions that are subject to taxes lower than the U.S. federal statutory tax rate, tax benefits related to stock-based compensation, the benefit of the U.S. federal research tax credit, and for fiscal year 2019, the reduction in our provisional U.S. tax reform transition tax amount. In December 2017, the SEC issued guidance that allows companies to record provisional amounts for the tax effects of the Tax Cuts and Job Acts, or TCJA, during a measurement period not to exceed one year. The TCJA was effective in the fourth quarter of fiscal year 2018 and we have recorded provisional amounts based on reasonable estimates for those tax effects. For the third quarter of fiscal year 2019, we reduced our provisional transition tax amount based on proposed regulations issued on August 1, 2018. We expect to complete our analysis of these provisional amounts in our fourth quarter of fiscal year 2019 based on further guidance on accounting interpretations from the FASB and application of the law from the U.S. Department of Treasury, which may further impact our provisional estimates. The TCJA subjects a U.S. corporation to tax on its global intangible low-taxed income, or GILTI. Under U.S. GAAP, we can make an accounting policy election to either treat taxes due on the GILTI as a current period expense or factor such amounts into our measurement of deferred taxes. Given the complexity of the GILTI provisions, we are still evaluating its effects and have not yet determined our accounting policy. We expect to complete our analysis in the fourth quarter of fiscal year 2019. For the third quarter of fiscal year 2019, as we are still evaluating the effects of the GILTI provisions, we have included tax expense related to GILTI for current-year operations in our estimated annual effective tax rate and have not provided for GILTI on deferred items. For the first nine months of fiscal year 2019, there have been no material changes to our tax years that remain subject to examination by major tax jurisdictions. Additionally, there have been no material changes to our unrecognized tax benefits and any related interest or penalties since the fiscal year ended January 28, 2018, other than the aforementioned reduction in our provisional U.S. tax reform transition tax amount. While we believe that we have adequately provided for all uncertain tax positions, or tax positions where we believe it is not more-likely-than-not that the position will be sustained upon review, amounts asserted by tax authorities could be greater or less than our accrued position. Accordingly, our provisions on federal, state and foreign tax related matters to be recorded in the future may change as revised estimates are made or the underlying matters are settled or otherwise resolved with the respective tax authorities. As of October 28, 2018, we do not believe that our estimates, as otherwise provided for, on such tax positions will significantly increase or decrease within the next twelve months.

Income Taxes

We recognized an income tax benefit of $149 million and $3 million for the third quarter and first nine months of fiscal year 2019, respectively, and income tax expense of $58 million and $189 million for the third quarter and first nine months of fiscal year 2018, respectively. Income tax benefit as a percentage of income before income tax was 13.8% and nominal for the third quarter and first nine months of fiscal year 2019, respectively, and income tax expense as a percentage of income before tax was 6.5% and 8.9% for the third quarter and first nine months of fiscal year 2018, respectively.

The decrease in our effective tax rate for the third quarter and first nine months of fiscal year 2019 as compared to the same periods in the prior fiscal year was primarily due to a decrease in the U.S. statutory tax rate from 35% to 21% as a result of U.S. tax reform, and a $138 million reduction in our provisional U.S. tax reform transition tax amount in the third quarter of fiscal year 2019, partially offset by a decrease in the impact of tax benefits from stock-based compensation.

Our effective tax rates for the first nine months of fiscal years 2019 and 2018 were nominal and 8.9%, respectively, and were lower than the U.S. federal statutory rates of 21% and 33.9%, for fiscal years 2019 and 2018, respectively, due to income earned in jurisdictions that are subject to taxes lower than the U.S. federal statutory tax rate, tax benefits related to stock-based compensation, the benefit of the U.S. federal research tax credit, and for fiscal year 2019, the reduction in our provisional U.S. tax reform transition tax amount.

In December 2017, the SEC issued guidance that allows companies to record provisional amounts for the tax effects of the Tax Cuts and Job Acts, or TCJA, during a measurement period not to exceed one year. The TCJA was effective in the fourth quarter of fiscal year 2018 and we have recorded provisional amounts based on reasonable estimates for those tax effects. For the third quarter of fiscal year 2019, we reduced our provisional transition tax amount based on proposed regulations issued on August 1, 2018. We expect to complete our analysis of these provisional amounts in our fourth quarter of fiscal year 2019 based on further guidance on accounting interpretations from the FASB and application of the law from the U.S. Department of Treasury, which may further impact our provisional estimates.

The TCJA subjects a U.S. corporation to tax on its global intangible low-taxed income, or GILTI. Under U.S. GAAP, we can make an accounting policy election to either treat taxes due on the GILTI as a current period expense or factor such amounts into our measurement of deferred taxes. Given the complexity of the GILTI provisions, we are still evaluating its effects and have not yet determined our accounting policy. We expect to complete our analysis in the fourth quarter of fiscal year 2019. For the third quarter of fiscal year 2019, as we are still evaluating the effects of the GILTI provisions, we have included tax expense related to GILTI for current-year operations in our estimated annual effective tax rate and have not provided for GILTI on deferred items.

For the first nine months of fiscal year 2019, there have been no material changes to our tax years that remain subject to examination by major tax jurisdictions. Additionally, there have been no material changes to our unrecognized tax benefits and any related interest or penalties since the fiscal year ended January 28, 2018, other than the aforementioned reduction in our provisional U.S. tax reform transition tax amount.

While we believe that we have adequately provided for all uncertain tax positions, or tax positions where we believe it is not more-likely-than-not that the position will be sustained upon review, amounts asserted by tax authorities could be greater or less than our accrued position. Accordingly, our provisions on federal, state and foreign tax related matters to be recorded in the future may change as revised estimates are made or the underlying matters are settled or otherwise resolved with the respective tax authorities. As of October 28, 2018, we do not believe that our estimates, as otherwise provided for, on such tax positions will significantly increase or decrease within the next twelve months.