Consolidated Statements of Income - USD ($) shares in Millions, $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Income Statement [Abstract]
REVENUE	$ 3,578.1	$ 3,443.4	$ 10,631.3	$ 10,420.9
Salary and service costs	2,586.5	2,476.1	7,747.2	7,533.9
Occupancy and other costs	288.6	281.0	877.9	874.2
Real estate and other repositioning costs	0.0	0.0	191.5	0.0
Charges arising from the effects of the war in Ukraine	0.0	0.0	0.0	113.4
Gain on disposition of subsidiary	0.0	0.0	(78.8)	0.0
Cost of services	2,875.1	2,757.1	8,737.8	8,521.5
Selling, general and administrative expenses	89.8	86.4	278.1	294.0
Depreciation and amortization	52.4	53.9	157.4	164.8
Total Operating Expenses	3,017.3	2,897.4	9,173.3	8,980.3
OPERATING INCOME	560.8	546.0	1,458.0	1,440.6
Interest Expense	53.5	52.0	165.9	154.2
Interest Income	15.2	22.9	80.9	42.2
INCOME BEFORE INCOME TAXES AND INCOME FROM EQUITY METHOD INVESTMENTS	522.5	516.9	1,373.0	1,328.6
Income Tax Expense	136.1	134.7	360.7	383.3
Income From Equity Method Investments	1.9	1.1	3.1	2.6
NET INCOME	388.3	383.3	1,015.4	947.9
Net Income Attributed To Noncontrolling Interests	16.4	18.8	49.7	61.2
NET INCOME - OMNICOM GROUP INC.	$ 371.9	$ 364.5	$ 965.7	$ 886.7
Net Income Per Share - Omnicom Group Inc.:
Basic	$ 1.88	$ 1.78	$ 4.84	$ 4.30
Diluted	$ 1.86	$ 1.77	$ 4.78	$ 4.27
Weighted Average Shares:
Basic	198.1	205.0	199.7	206.2
Diluted	199.9	206.3	202.0	207.6