Consolidated Statements of Income - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Income Statement [Abstract]
Revenue	$ 14,289.4	$ 13,171.1	$ 14,953.7
Salary and service costs	10,402.0	9,572.8	10,972.2
Occupancy and other costs	1,148.2	1,138.5	1,221.8
Gain on disposition of subsidiary	(50.5)	0.0	0.0
COVID-19 repositioning costs	0.0	277.9	0.0
Cost of services	11,499.7	10,989.2	12,194.0
Selling, general and administrative expenses	379.7	360.5	405.9
Depreciation and amortization	212.1	222.6	231.5
Operating Expenses	12,091.5	11,572.3	12,831.4
Operating Profit	2,197.9	1,598.8	2,122.3
Interest Expense	236.4	221.8	244.3
Interest Income	27.3	32.3	60.3
Income Before Income Taxes and Income (Loss) From Equity Method Investments	1,988.8	1,409.3	1,938.3
Income Tax Expense	488.7	381.7	504.4
Income (Loss) From Equity Method Investments	7.5	(6.8)	2.0
Net Income	1,507.6	1,020.8	1,435.9
Net Income Attributed To Noncontrolling Interests	99.8	75.4	96.8
Net Income - Omnicom Group Inc.	$ 1,407.8	$ 945.4	$ 1,339.1
Net Income Per Share - Omnicom Group Inc.:
Basic	$ 6.57	$ 4.38	$ 6.09
Diluted	$ 6.53	$ 4.37	$ 6.06