Income Taxes	9 Months Ended
Sep. 30, 2015
Income Tax Disclosure [Abstract]
Income Taxes	Income Taxes Our effective income tax rates were 24.1% and 23.9% for the three and nine months ended September 30, 2015, respectively. Our effective income tax rates were 24.7% and 24.0% for the three and nine months ended September 30, 2014, respectively. Our effective income tax rate is based upon estimated income before provision for income taxes for the year, composition of the income in different countries, and adjustments, if any, in the applicable quarterly periods for potential tax consequences, benefits and/or resolutions of tax audits or other tax contingencies. For the three and nine months ended September 30, 2015, the effective income tax rate varied from the statutory income tax rate principally as a result of the mix of income attributable to foreign versus domestic jurisdictions and state taxes. Our aggregate income tax rate in foreign jurisdictions is lower than our income tax rate in the United States; substantially all of our income before provision for income taxes from foreign operations has been earned by our Irish subsidiaries. For the three and nine months ended September 30, 2014, the effective income tax rate varied from the statutory income tax rate principally as a result of the mix of income attributable to foreign versus domestic jurisdictions and state taxes. On December 19, 2014, the Tax Increase Prevention Act was signed into law. Some of the provisions were retroactive to January 1, 2014 including an extension of the U.S. federal tax credit for increasing research activities through December 31, 2014. Our effective income tax rates for the three and nine months ended September 30, 2015 and 2014 do not reflect any federal tax credit for increasing research activities. Our effective income tax rate decreased in the three months ended September 30, 2015 from the three months ended September 30, 2014 due primarily to a decrease in tax contingency reserves and lower state taxes partially offset by a lower tax rate differential for international jurisdictions. There were also differences in discrete items, the net impact of which is immaterial. Our effective income tax rate for the nine months ended September 30, 2015 was consistent with our effective income tax rate for the nine months ended September 30, 2014. We are routinely under audit by the Internal Revenue Service (the “IRS”). We have concluded all U.S. federal income tax matters for years through 2008. In the third quarter of 2012, the IRS commenced a federal income tax audit for the tax years 2009 and 2010, which is expected to be completed in late 2015. In the first quarter of 2015, the IRS commenced a federal income tax audit for the tax year 2011, which is still in the early stage for information gathering. We also have income tax audits in process in numerous state, local and international jurisdictions. In our international jurisdictions that comprise a significant portion of our operations, the years that may be examined vary, with the earliest year being 2005. Based on the timing and outcome of examinations of EMC, the result of the expiration of statutes of limitations for specific jurisdictions or the timing and result of ruling requests from taxing authorities, it is reasonably possible that the related unrecognized tax benefits could change from those recorded in our consolidated balance sheets. We anticipate that several of these audits may be finalized within the next twelve months. While we expect the amount of unrecognized tax benefits to change in the next twelve months, we do not expect the change to have a significant impact on our consolidated results of operations or financial position.

Income Taxes

Our effective income tax rates were 24.1% and 23.9% for the three and nine months ended September 30, 2015, respectively. Our effective income tax rates were 24.7% and 24.0% for the three and nine months ended September 30, 2014, respectively. Our effective income tax rate is based upon estimated income before provision for income taxes for the year, composition of the income in different countries, and adjustments, if any, in the applicable quarterly periods for potential tax consequences, benefits and/or resolutions of tax audits or other tax contingencies. For the three and nine months ended September 30, 2015, the effective income tax rate varied from the statutory income tax rate principally as a result of the mix of income attributable to foreign versus domestic jurisdictions and state taxes. Our aggregate income tax rate in foreign jurisdictions is lower than our income tax rate in the United States; substantially all of our income before provision for income taxes from foreign operations has been earned by our Irish subsidiaries. For the three and nine months ended September 30, 2014, the effective income tax rate varied from the statutory income tax rate principally as a result of the mix of income attributable to foreign versus domestic jurisdictions and state taxes. On December 19, 2014, the Tax Increase Prevention Act was signed into law. Some of the provisions were retroactive to January 1, 2014 including an extension of the U.S. federal tax credit for increasing research activities through December 31, 2014. Our effective income tax rates for the three and nine months ended September 30, 2015 and 2014 do not reflect any federal tax credit for increasing research activities.

Our effective income tax rate decreased in the three months ended September 30, 2015 from the three months ended September 30, 2014 due primarily to a decrease in tax contingency reserves and lower state taxes partially offset by a lower tax rate differential for international jurisdictions. There were also differences in discrete items, the net impact of which is immaterial. Our effective income tax rate for the nine months ended September 30, 2015 was consistent with our effective income tax rate for the nine months ended September 30, 2014.

We are routinely under audit by the Internal Revenue Service (the “IRS”). We have concluded all U.S. federal income tax matters for years through 2008. In the third quarter of 2012, the IRS commenced a federal income tax audit for the tax years 2009 and 2010, which is expected to be completed in late 2015. In the first quarter of 2015, the IRS commenced a federal income tax audit for the tax year 2011, which is still in the early stage for information gathering. We also have income tax audits in process in numerous state, local and international jurisdictions. In our international jurisdictions that comprise a significant portion of our operations, the years that may be examined vary, with the earliest year being 2005. Based on the timing and outcome of examinations of EMC, the result of the expiration of statutes of limitations for specific jurisdictions or the timing and result of ruling requests from taxing authorities, it is reasonably possible that the related unrecognized tax benefits could change from those recorded in our consolidated balance sheets. We anticipate that several of these audits may be finalized within the next twelve months. While we expect the amount of unrecognized tax benefits to change in the next twelve months, we do not expect the change to have a significant impact on our consolidated results of operations or financial position.