Consolidated Statements of Income - USD ($) shares in Millions, $ in Millions	3 Months Ended
	Mar. 31, 2026	Mar. 31, 2025
Income Statement [Abstract]
Revenue	$ 6,242.9	$ 3,690.4
Salary and service costs	4,639.6	2,746.3
Occupancy and other costs	527.3	314.6
Severance and repositioning costs	4.1	0.0
Loss on assets held for sale and dispositions	34.3	0.0
Cost of services	5,205.3	3,060.9
Selling, general and administrative expenses	224.5	117.9
Depreciation and amortization	166.9	59.0
Total Operating Expenses	5,596.7	3,237.8
Operating Income	646.2	452.6
Interest Expense	119.0	59.1
Interest Income	47.0	29.7
Income Before Income Taxes and Income (Loss) From Equity Method Investments	574.2	423.2
Income Tax Expense	154.6	120.7
Income (Loss) From Equity Method Investments	(0.9)	0.9
Net Income	418.7	303.4
Net Income Attributed To Noncontrolling Interests	13.5	15.7
Net Income - Omnicom Group Inc.	$ 405.2	$ 287.7
Net Income Per Share - Omnicom Group Inc.:
Basic	$ 1.36	$ 1.46
Diluted	$ 1.35	$ 1.45
Weighted Average Shares:
Basic	298.1	196.7
Diluted	299.2	198.3