Consolidated Statements of Income (USD $) In Millions, except Per Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
REVENUE	$ 13,872.5	$ 12,542.5	$ 11,720.7
OPERATING EXPENSES	12,201.4	11,082.3	10,345.8
OPERATING INCOME	1,671.1	1,460.2	1,374.9
INTEREST EXPENSE	158.1	134.7	122.2
INTEREST INCOME	36.0	24.9	21.5
INCOME BEFORE INCOME TAXES AND INCOME FROM EQUITY METHOD INVESTMENTS	1,549.0	1,350.4	1,274.2
INCOME TAX EXPENSE	505.8	460.2	433.6
INCOME FROM EQUITY METHOD INVESTMENTS	17.2	33.5	30.8
NET INCOME	1,060.4	923.7	871.4
LESS: NET INCOME ATTRIBUTED TO NONCONTROLLING INTERESTS	107.8	96.0	78.4
NET INCOME - OMNICOM GROUP INC.	$ 952.6	$ 827.7	$ 793.0
Net Income Per Share - Omnicom Group Inc.:
Basic	$ 3.38	$ 2.74	$ 2.54
Diluted	$ 3.33	$ 2.70	$ 2.53