Presentation of Financial Statements	3 Months Ended
Presentation of Financial Statements	Mar. 31, 2015
Presentation of Financial Statements [Abstract]
Presentation of Financial Statements	Presentation of Financial Statements The terms “Omnicom,” the “Company,” “we,” “our” and “us” each refer to Omnicom Group Inc. and our subsidiaries, unless the context indicates otherwise. The accompanying unaudited condensed consolidated financial statements were prepared in accordance with generally accepted accounting principles in the United States (“U.S. GAAP” or “GAAP”) for interim financial information and Article 10 of Regulation S-X of the Securities and Exchange Commission. Accordingly, certain information and footnote disclosure have been condensed or omitted. In our opinion, the accompanying unaudited condensed consolidated financial statements reflect all adjustments, consisting of normal recurring accruals, considered necessary for a fair presentation, in all material respects, of the information contained herein. Certain reclassifications have been made to the prior year financial information to conform to the current year presentation. These unaudited condensed consolidated financial statements should be read in conjunction with our Annual Report on Form 10-K for the year ended December 31, 2014 (“2014 10-K”). Results for the interim periods are not necessarily indicative of results that may be expected for the year.

The entire disclosure for organization, consolidation and basis of presentation of financial statements disclosure.