Condensed Consolidated Statements of Income (USD $) In Millions, except Per Share data, unless otherwise specified	3 Months Ended
Mar. 31, 2015	Mar. 31, 2014
Revenue	$ 3,469.2us-gaap_Revenues	$ 3,502.2us-gaap_Revenues
Operating Expenses	3,091.5us-gaap_OperatingExpenses	3,119.5us-gaap_OperatingExpenses
Operating Income	377.7us-gaap_OperatingIncomeLoss	382.7us-gaap_OperatingIncomeLoss
Interest Expense	43.6us-gaap_InterestExpense	47.7us-gaap_InterestExpense
Interest Income	9.4us-gaap_InvestmentIncomeInterest	8.7us-gaap_InvestmentIncomeInterest
Income Before Income Taxes and Income From Equity Method Investments	343.5	343.7
Income Tax Expense	112.7us-gaap_IncomeTaxExpenseBenefit	116.3us-gaap_IncomeTaxExpenseBenefit
Income (Loss) From Equity Method Investments	(1.0)	0.6
Net Income	229.8us-gaap_ProfitLoss	228.0us-gaap_ProfitLoss
Net Income Attributed To Noncontrolling Interests	20.7	22.5
Net Income - Omnicom Group Inc.	$ 209.1us-gaap_NetIncomeLoss	$ 205.5us-gaap_NetIncomeLoss
Net Income Per Share - Omnicom Group Inc.:
Basic	$ 0.84us-gaap_EarningsPerShareBasic	$ 0.78us-gaap_EarningsPerShareBasic
Diluted	$ 0.83us-gaap_EarningsPerShareDiluted	$ 0.77us-gaap_EarningsPerShareDiluted
Dividends Declared Per Common Share	$ 0.50	$ 0.40

Aggregate dividends declared during the period for each share of common stock outstanding.

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