Consolidated Statements of Income - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Income Statement [Abstract]
Revenue	$ 15,689.1	$ 14,692.2	$ 14,289.1
Salary and service costs	11,432.5	10,701.2	10,325.9
Occupancy and other costs	1,274.4	1,168.8	1,168.6
Real estate and other repositioning costs	57.8	191.5	0.0
Charges arising from the effects of the war in Ukraine	0.0	0.0	113.4
Gain on disposition of subsidiary	0.0	(78.8)	0.0
Cost of services	12,764.7	11,982.7	11,607.9
Selling, general and administrative expenses	408.1	393.7	378.5
Depreciation and amortization	241.7	211.1	219.4
Operating Expenses	13,414.5	12,587.5	12,205.8
Operating Income	2,274.6	2,104.7	2,083.3
Interest Expense	247.9	218.5	208.6
Interest Income	100.9	106.7	70.7
Income Before Income Taxes and Income From Equity Method Investments	2,127.6	1,992.9	1,945.4
Income Tax Expense	560.5	524.9	546.8
Income From Equity Method Investments	6.9	5.2	5.2
Net Income	1,574.0	1,473.2	1,403.8
Net Income Attributed To Noncontrolling Interests	93.4	81.8	87.3
Net Income - Omnicom Group Inc.	$ 1,480.6	$ 1,391.4	$ 1,316.5
Net Income Per Share - Omnicom Group Inc.:
Basic	$ 7.54	$ 6.98	$ 6.40
Diluted	$ 7.46	$ 6.91	$ 6.36