Income Taxes (Notes)	9 Months Ended
Sep. 30, 2018
Income Tax Disclosure [Abstract]
Income Taxes	Income Taxes For the three and nine months ended September 30, 2018, our effective income tax rates were negatively impacted by losses in certain foreign jurisdictions where we receive no tax benefit due to 100% valuation allowances, by losses on sales of businesses, and the classification of certain assets as held for sale, for which we received a minimal tax benefit, by tax expense associated with the change to our assertion regarding the permanent reinvestment of undistributed earnings attributable to certain foreign subsidiaries, and by tax expense related to the true-up of our December 31, 2017 tax reform estimates as permitted by SEC Staff issued Staff Accounting Bulletin No. 118 ("SAB 118"). This was partially offset by a tax benefit related to foreign tax credits from a distribution of unremitted earnings. The nine months ended September 30, 2018 also included research and development credits based on the conclusion of multi-year studies. Public Law 115-97, commonly referred to as the Tax Cuts and Jobs Act (the "Tax Act") was signed into law on December 22, 2017. The Tax Act legislated many new tax provisions which have impacted our operations. At December 31, 2017, provisional amounts were recorded as permitted by SAB 118. As of September 30, 2018, we have finalized our calculations of the impact of the Tax Act and have revised our estimates as required by SAB 118. This resulted in a net increase of $16.7, primarily attributable to our estimate of the tax imposed on the deemed repatriation of unremitted foreign earnings. The Company has historically asserted that its unremitted foreign earnings are permanently reinvested, and therefore has not recorded any deferred taxes on such amounts. During the third quarter ended September 30, 2018, as a result of our increased debt and associated servicing commitments in connection with the Acxiom Acquisition that was consummated on October 1, 2018, the Company re-evaluated its global cash needs and as a result determined that approximately $440.0 of undistributed foreign earnings from certain international entities are no longer subject to the permanent reinvestment assertion. We recorded a tax expense of $17.3 representing our estimate of the tax costs associated with this change to our assertion. We have not changed our permanent reinvestment assertion with respect to any other international entities as the related historical earnings and profits will fund international operations and investments. The Tax Act imposed a new tax on certain foreign earnings generated in 2018 and forward. These global intangible low-taxed income ("GILTI") tax rules are complex. U.S. GAAP allows us to choose an accounting policy which treats the U.S. tax under GILTI provisions as either a current expense, as incurred, or as a component of the Company’s measurement of deferred taxes. The Company has elected to account for the GILTI tax as a current expense. We have various tax years under examination by tax authorities in various countries, and in various states, such as New York, in which we have significant business operations. It is not yet known whether these examinations will, in the aggregate, result in our paying additional taxes. We believe our tax reserves are adequate in relation to the potential for additional assessments in each of the jurisdictions in which we are subject to taxation. We regularly assess the likelihood of additional tax assessments in those jurisdictions and, if necessary, adjust our reserves as additional information or events require. The total amount of gross unrecognized tax benefits as of September 30, 2018 was $342.5. The amount of unrecognized tax benefits that, if recognized, would affect the effective tax rate is $317.2. During the three and nine months ended September 30, 2018, the net increase to our unrecognized tax benefits was $36.6 and $70.5, respectively. The increase is primarily due to tax positions taken during a prior year. With respect to all tax years open to examination by U.S. federal, various state and local, and non-U.S. tax authorities, we currently anticipate that total unrecognized tax benefits will decrease by an amount between $30.0 and $40.0 in the next twelve months, a portion of which will affect our effective income tax rate, primarily as a result of the settlement of tax examinations and the lapsing of statutes of limitations. We are effectively settled with respect to U.S. federal income tax audits through 2012, with the exception of 2009. With limited exceptions, we are no longer subject to state and local income tax audits for years prior to 2007 or non-U.S. income tax audits for years prior to 2006.

Income Taxes

For the three and nine months ended September 30, 2018, our effective income tax rates were negatively impacted by losses in certain foreign jurisdictions where we receive no tax benefit due to 100% valuation allowances, by losses on sales of businesses, and the classification of certain assets as held for sale, for which we received a minimal tax benefit, by tax expense associated with the change to our assertion regarding the permanent reinvestment of undistributed earnings attributable to certain foreign subsidiaries, and by tax expense related to the true-up of our December 31, 2017 tax reform estimates as permitted by SEC Staff issued Staff Accounting Bulletin No. 118 ("SAB 118"). This was partially offset by a tax benefit related to foreign tax credits from a distribution of unremitted earnings. The nine months ended September 30, 2018 also included research and development credits based on the conclusion of multi-year studies.

Public Law 115-97, commonly referred to as the Tax Cuts and Jobs Act (the "Tax Act") was signed into law on December 22, 2017. The Tax Act legislated many new tax provisions which have impacted our operations. At December 31, 2017, provisional amounts were recorded as permitted by SAB 118. As of September 30, 2018, we have finalized our calculations of the impact of the Tax Act and have revised our estimates as required by SAB 118. This resulted in a net increase of $16.7, primarily attributable to our estimate of the tax imposed on the deemed repatriation of unremitted foreign earnings.

The Company has historically asserted that its unremitted foreign earnings are permanently reinvested, and therefore has not recorded any deferred taxes on such amounts. During the third quarter ended September 30, 2018, as a result of our increased debt and associated servicing commitments in connection with the Acxiom Acquisition that was consummated on October 1, 2018, the Company re-evaluated its global cash needs and as a result determined that approximately $440.0 of undistributed foreign earnings from certain international entities are no longer subject to the permanent reinvestment assertion. We recorded a tax expense of $17.3 representing our estimate of the tax costs associated with this change to our assertion. We have not changed our permanent reinvestment assertion with respect to any other international entities as the related historical earnings and profits will fund international operations and investments.

The Tax Act imposed a new tax on certain foreign earnings generated in 2018 and forward. These global intangible low-taxed income ("GILTI") tax rules are complex. U.S. GAAP allows us to choose an accounting policy which treats the U.S. tax under GILTI provisions as either a current expense, as incurred, or as a component of the Company’s measurement of deferred taxes. The Company has elected to account for the GILTI tax as a current expense.

We have various tax years under examination by tax authorities in various countries, and in various states, such as New York, in which we have significant business operations. It is not yet known whether these examinations will, in the aggregate, result in our paying additional taxes. We believe our tax reserves are adequate in relation to the potential for additional assessments in each of the jurisdictions in which we are subject to taxation. We regularly assess the likelihood of additional tax assessments in those jurisdictions and, if necessary, adjust our reserves as additional information or events require.

The total amount of gross unrecognized tax benefits as of September 30, 2018 was $342.5. The amount of unrecognized tax benefits that, if recognized, would affect the effective tax rate is $317.2. During the three and nine months ended September 30, 2018, the net increase to our unrecognized tax benefits was $36.6 and $70.5, respectively. The increase is primarily due to tax positions taken during a prior year.

With respect to all tax years open to examination by U.S. federal, various state and local, and non-U.S. tax authorities, we currently anticipate that total unrecognized tax benefits will decrease by an amount between $30.0 and $40.0 in the next twelve months, a portion of which will affect our effective income tax rate, primarily as a result of the settlement of tax examinations and the lapsing of statutes of limitations.

We are effectively settled with respect to U.S. federal income tax audits through 2012, with the exception of 2009. With limited exceptions, we are no longer subject to state and local income tax audits for years prior to 2007 or non-U.S. income tax audits for years prior to 2006.