Consolidated Statements of Income - USD ($) shares in Millions, $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2025	Jun. 30, 2024	Jun. 30, 2025	Jun. 30, 2024
Income Statement [Abstract]
Revenue	$ 4,015.6	$ 3,853.8	$ 7,706.0	$ 7,484.3
Salary and service costs	2,932.6	2,800.1	5,678.9	5,492.7
Occupancy and other costs	325.9	314.2	640.5	628.3
Repositioning costs	88.8	57.8	88.8	57.8
Cost of services	3,347.3	3,172.1	6,408.2	6,178.8
Selling, general and administrative expenses	170.4	111.0	288.3	196.3
Depreciation and amortization	58.7	60.4	117.7	120.0
Total Operating Expenses	3,576.4	3,343.5	6,814.2	6,495.1
Operating Income	439.2	510.3	891.8	989.2
Interest Expense	62.6	62.7	121.7	116.5
Interest Income	21.9	21.0	51.6	48.0
Income Before Income Taxes and Income From Equity Method Investments	398.5	468.6	821.7	920.7
Income Tax Expense	120.5	123.7	241.2	239.7
Income From Equity Method Investments	(0.2)	3.3	0.7	4.2
Net Income	277.8	348.2	581.2	685.2
Net Income Attributed To Noncontrolling Interests	20.2	20.1	35.9	38.5
Net Income - Omnicom Group Inc.	$ 257.6	$ 328.1	$ 545.3	$ 646.7
Net Income Per Share - Omnicom Group Inc.:
Basic	$ 1.32	$ 1.67	$ 2.78	$ 3.28
Diluted	$ 1.31	$ 1.65	$ 2.77	$ 3.24
Weighted Average Shares:
Basic	194.9	195.9	195.8	196.9
Diluted	196.0	198.5	197.1	199.3