Consolidated Statements of Comprehensive Income - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Statement of Comprehensive Income [Abstract]
Net income	$ 1,574.0	$ 1,473.2	$ 1,403.8
Cash flow hedge:
Amortization of loss included in interest expense	4.4	5.6	5.6
Income tax effect	(1.3)	(1.6)	(1.6)
Cash flow hedge, net of tax	3.1	4.0	4.0
Pension and other postemployment benefits:
Unrecognized actuarial gains (losses) and prior service cost for the period	18.7	(6.8)	58.4
Amortization of prior service cost and actuarial (gains) losses	5.8	4.8	10.7
Income tax effect	(7.3)	0.6	(20.0)
Pension and other postemployment benefits, net of tax	17.2	(1.4)	49.1
Foreign currency translation adjustment	(171.7)	98.9	(255.2)
Other Comprehensive Income (Loss)	(151.4)	101.5	(202.1)
Comprehensive Income	1,422.6	1,574.7	1,201.7
Comprehensive Income Attributed To Noncontrolling Interests	80.3	83.0	70.8
Comprehensive Income - Omnicom Group Inc.	$ 1,342.3	$ 1,491.7	$ 1,130.9