Consolidated Statements of Income - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2025	Dec. 31, 2024	Dec. 31, 2023
Income Statement [Abstract]
Revenue	$ 17,271.9	$ 15,689.1	$ 14,692.2
Salary and service costs	12,644.0	11,432.5	10,701.2
Occupancy and other costs	1,366.7	1,274.4	1,168.8
Severance and repositioning costs	1,247.0	57.8	191.5
Loss (gain) on assets held for sale and dispositions	547.1	0.0	(78.8)
Cost of services	15,804.8	12,764.7	11,982.7
Selling, general and administrative expenses	745.7	408.1	393.7
Depreciation and amortization	276.7	241.7	211.1
Total Operating Expenses	16,827.2	13,414.5	12,587.5
Operating Income	444.7	2,274.6	2,104.7
Interest Expense	263.4	247.9	218.5
Interest Income	96.9	100.9	106.7
Income Before Income Taxes and Income From Equity Method Investments	278.2	2,127.6	1,992.9
Income Tax Expense	242.2	560.5	524.9
Income From Equity Method Investments	7.7	6.9	5.2
Net Income	43.7	1,574.0	1,473.2
Net Income Attributed To Noncontrolling Interests	98.2	93.4	81.8
Net Income (Loss) - Omnicom Group Inc.	$ (54.5)	$ 1,480.6	$ 1,391.4
Net Income (Loss) Per Share - Omnicom Group Inc.:
Basic	$ (0.27)	$ 7.54	$ 6.98
Diluted	$ (0.27)	$ 7.46	$ 6.91