Consolidated Statements of Income - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Income Statement [Abstract]
Revenue	$ 14,692.2	$ 14,289.1	$ 14,289.4
Salary and service costs	10,701.2	10,325.9	10,402.0
Occupancy and other costs	1,168.8	1,168.6	1,148.2
Real estate and other repositioning costs	191.5	0.0	0.0
Charges arising from the effects of the war in Ukraine	0.0	113.4	0.0
Gain on disposition of subsidiary	(78.8)	0.0	(50.5)
Cost of services	11,982.7	11,607.9	11,499.7
Selling, general and administrative expenses	393.7	378.5	379.7
Depreciation and amortization	211.1	219.4	212.1
Operating Expenses	12,587.5	12,205.8	12,091.5
Operating Income	2,104.7	2,083.3	2,197.9
Interest Expense	218.5	208.6	236.4
Interest Income	106.7	70.7	27.3
Income Before Income Taxes and Income From Equity Method Investments	1,992.9	1,945.4	1,988.8
Income Tax Expense	524.9	546.8	488.7
Income From Equity Method Investments	5.2	5.2	7.5
Net Income	1,473.2	1,403.8	1,507.6
Net Income Attributed To Noncontrolling Interests	81.8	87.3	99.8
Net Income - Omnicom Group Inc.	$ 1,391.4	$ 1,316.5	$ 1,407.8
Net Income Per Share - Omnicom Group Inc.:
Basic	$ 6.98	$ 6.40	$ 6.57
Diluted	$ 6.91	$ 6.36	$ 6.53