Income Taxes	3 Months Ended
Apr. 28, 2019
Income Tax Disclosure [Abstract]
Income Taxes	Income Taxes We recognized an income tax benefit of $5 million for the first quarter of fiscal year 2020 and income tax expense of $67 million for the first quarter of fiscal year 2019. The income tax benefit as a percentage of income before income tax was 1.3% for the first quarter of fiscal year 2020 and income tax expense as a percentage of income before tax was 5.1% for the first quarter of fiscal year 2019. The decrease in our effective tax rate for the first quarter of fiscal year 2020 as compared to the same period in the prior fiscal year was primarily due to a decrease in the amount of earnings subject to United States tax, and an increase in the impact of tax benefits from stock-based compensation and the U.S. federal research tax credit. Our effective tax rates for the first quarter of fiscal years 2020 and 2019 were (1.3)% and 5.1%, respectively, and were lower than the U.S. federal statutory rate of 21%, 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, and the benefit of the U.S. federal research tax credit. For the first quarter of fiscal year 2020, 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 27, 2019. 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 April 28, 2019, 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 $5 million for the first quarter of fiscal year 2020 and income tax expense of $67 million for the first quarter of fiscal year 2019. The income tax benefit as a percentage of income before income tax was 1.3% for the first quarter of fiscal year 2020 and income tax expense as a percentage of income before tax was 5.1% for the first quarter of fiscal year 2019.

The decrease in our effective tax rate for the first quarter of fiscal year 2020 as compared to the same period in the prior fiscal year was primarily due to a decrease in the amount of earnings subject to United States tax, and an increase in the impact of tax benefits from stock-based compensation and the U.S. federal research tax credit.

Our effective tax rates for the first quarter of fiscal years 2020 and 2019 were (1.3)% and 5.1%, respectively, and were lower than the U.S. federal statutory rate of 21%, 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, and the benefit of the U.S. federal research tax credit.

For the first quarter of fiscal year 2020, 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 27, 2019.

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 April 28, 2019, 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.