Planned Acquisition of IPG by Omnicom (Details) $ in Millions	3 Months Ended	6 Months Ended
	Jun. 30, 2025 USD ($)	Jun. 30, 2025 USD ($)
Business Combination [Line Items]
Conversion ratio	0.344
Percentage of voting interests in post-merger entity - omnicom shareholders (as a percent)	60.60%	60.60%
Percentage of voting interests in post-merger entity - ipg shareholders (as a percent)	39.40%	39.40%
Loss on contract termination	$ 439.0
Loss on contract termination, (as percent)	50.00%	50.00%
IPG | Omnicom
Business Combination [Line Items]
Deal costs comprised of legal professional filing fees	$ 10.9	$ 15.7