Consolidated Statements of Comprehensive Income - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Statement of Comprehensive Income [Abstract]
NET INCOME	$ 409.9	$ 388.3	$ 1,095.1	$ 1,015.4
Cash flow hedge:
Amortization of loss included in interest expense	1.3	1.4	3.9	4.2
Income tax effect	(0.4)	(0.4)	(1.1)	(1.2)
Cash flow hedge, net of tax	0.9	1.0	2.8	3.0
Defined benefit pension plans and postemployment arrangements:
Amortization of prior service cost	1.2	1.0	3.6	3.1
Amortization of actuarial losses	0.3	0.2	0.8	0.6
Income tax effect	(1.0)	(0.9)	(3.3)	(1.7)
Defined benefit pension plans and postemployment arrangements, net of tax	0.5	0.3	1.1	2.0
Foreign currency translation adjustment	180.2	(110.4)	62.0	(34.2)
Other Comprehensive Income (Loss)	181.6	(109.1)	65.9	(29.2)
TOTAL COMPREHENSIVE INCOME	591.5	279.2	1,161.0	986.2
Comprehensive Income Attributed To Noncontrolling Interests	34.4	11.6	65.1	41.1
COMPREHENSIVE INCOME - OMNICOM GROUP INC.	$ 557.1	$ 267.6	$ 1,095.9	$ 945.1