Consolidated Statements of Comprehensive Income - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Statement of Comprehensive Income [Abstract]
Net income	$ 1,507.6	$ 1,020.8	$ 1,435.9
Cash flow hedge:
Amortization of loss included in interest expense	5.6	5.5	5.5
Income tax effect	(1.6)	(1.6)	(1.6)
Other comprehensive income (loss), Cash flow hedge	4.0	3.9	3.9
Defined benefit pension plans and postemployment arrangements:
Unrecognized actuarial gains (losses) and prior service cost for the period	28.3	(29.5)	(45.5)
Amortization of prior service cost and actuarial losses	18.1	13.9	8.7
Income tax effect	(13.6)	4.5	10.7
Other comprehensive income (loss), Defined benefit pension plans and postemployment arrangements	32.8	(11.1)	(26.1)
Foreign currency translation adjustment	(92.2)	(5.0)	74.9
Other Comprehensive Income ( Loss)	(55.4)	(12.2)	52.7
Comprehensive Income	1,452.2	1,008.6	1,488.6
Comprehensive Income Attributed To Noncontrolling Interests	82.9	79.5	96.3
Comprehensive Income - Omnicom Group Inc.	$ 1,369.3	$ 929.1	$ 1,392.3