Noncontrolling Interests (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Changes in Ownership Interests in Less Than 100% Owned Subsidiaries [Abstract]
Net income attributed to Omnicom Group Inc.	$ 1,391.4	$ 1,316.5	$ 1,407.8
Net transfers (to) from noncontrolling interests	(88.1)	(17.1)	(12.2)
Change from net income attributed to Omnicom Group Inc. and transfers (to) from noncontrolling interests	$ 1,303.3	$ 1,299.4	$ 1,395.6