Consolidated Statements of Comprehensive Income - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2025	Sep. 30, 2024
Statement of Comprehensive Income [Abstract]
Net Income	$ 360.4	$ 409.9	$ 941.6	$ 1,095.1
Cash flow hedge:
Amortization of loss included in interest expense	1.3	1.3	4.1	3.9
Income tax effect	(0.4)	(0.4)	(1.3)	(1.1)
Cash flow hedge, net of tax	0.9	0.9	2.8	2.8
Pension and other postemployment benefits:
Amortization of prior service cost	1.7	1.2	5.1	3.6
Amortization of actuarial losses	0.2	0.3	0.7	0.8
Income tax effect	(1.4)	(1.0)	(4.4)	(3.3)
Pension plans and other postemployment benefits, net of tax	0.5	0.5	1.4	1.1
Foreign currency translation adjustment	(60.6)	180.2	155.2	62.0
Other Comprehensive Income (Loss)	(59.2)	181.6	159.4	65.9
Comprehensive Income	301.2	591.5	1,101.0	1,161.0
Comprehensive Income Attributed To Noncontrolling Interests	16.1	34.4	65.6	65.1
Comprehensive Income - Omnicom Group Inc.	$ 285.1	$ 557.1	$ 1,035.4	$ 1,095.9