CONDENSED CONSOLIDATED STATEMENTS OF INCOME (USD $) In Millions, except Per Share data	3 Months Ended		6 Months Ended
	Jun. 30, 2011	Jun. 30, 2010	Jun. 30, 2011	Jun. 30, 2010
Income Statement [Abstract]
REVENUE	$ 3,487.4	$ 3,041.2	$ 6,638.8	$ 5,961.2
OPERATING EXPENSES	2,999.3	2,625.8	5,828.5	5,254.8
OPERATING INCOME	488.1	415.4	810.3	706.4
INTEREST EXPENSE	36.9	29.9	78.8	59.7
INTEREST INCOME	9.3	6.2	18.9	11.9
INCOME BEFORE INCOME TAXES AND INCOME FROM EQUITY METHOD INVESTMENTS	460.5	391.7	750.4	658.6
INCOME TAX EXPENSE	158.1	133.2	231.9	223.9
INCOME FROM EQUITY METHOD INVESTMENTS	4.8	10.3	5.9	15.0
NET INCOME	307.2	268.8	524.4	449.7
LESS: NET INCOME ATTRIBUTED TO NONCONTROLLING INTERESTS	32.1	25.5	47.4	43.0
NET INCOME - OMNICOM GROUP INC.	$ 275.1	$ 243.3	$ 477.0	$ 406.7
NET INCOME PER COMMON SHARE - OMNICOM GROUP INC.:
Basic	$ 0.98	$ 0.80	$ 1.68	$ 1.32
Diluted	$ 0.96	$ 0.79	$ 1.65	$ 1.30
DIVIDENDS DECLARED PER COMMON SHARE	$ 0.25	$ 0.2	$ 0.5	$ 0.4