v3.26.1
Business Combinations (Details) - USD ($)
$ in Millions
3 Months Ended 6 Months Ended
Nov. 26, 2025
Jun. 30, 2026
Jun. 30, 2025
Jun. 30, 2026
Jun. 30, 2025
Dec. 31, 2025
Dec. 31, 2024
Liabilities Assumed [Abstract]              
Goodwill   $ 18,740.7 $ 11,001.8 $ 18,740.7 $ 11,001.8 $ 18,641.4 $ 10,677.4
Intangible assets, Gross Carrying Value   5,935.9   5,935.9   6,004.2  
Integration and acquisition related costs   40.1 $ 66.0 99.5 $ 99.8    
Trade Names              
Liabilities Assumed [Abstract]              
Intangible assets, Gross Carrying Value   922.5   922.5   929.9  
Customer Relationships              
Liabilities Assumed [Abstract]              
Intangible assets, Gross Carrying Value   4,366.8   4,366.8   4,389.5  
Technology and Other              
Liabilities Assumed [Abstract]              
Intangible assets, Gross Carrying Value   357.6   357.6   $ 409.2  
IPG              
Business Combination [Line Items]              
Omnicom shares issued, IPG acquisition 124,352,188            
Purchase Consideration [Abstract]              
Fair value of shares issued to IPG shareholders1 $ 8,891.2            
Cash paid for fractional shares 0.3            
Fair value of equity awards2 2.0            
Total Consideration 8,893.5            
Assets Acquired [Abstract]              
Cash and Cash equivalents 1,080.6            
Accounts receivable 5,753.1            
Work in process 2,227.6            
Assets held for sale 266.1            
Other current Assets 566.8            
Property and equipment 251.6            
Operating lease right-of-use assets 598.9            
Equity Method Investments 32.1            
Intangible assets 4,578.8            
Other Assets 705.5            
Total Assets 16,061.1            
Liabilities Assumed [Abstract]              
Accounts payable 7,065.4            
Customer advances 715.8            
Short-term debt 42.4            
Liabilities held for sale 106.5            
Other current liabilities 1,696.7            
Long-term liabilities 432.7            
Long-term liability - operating leases 876.4            
Long-term debt 2,764.9            
Deferred tax liabilities, net 1,093.6            
Non-controlling interests 211.7            
Redeemable non-controlling interest 8.4            
Total Liabilities and Non-controlling interest 15,014.5            
Fair value of net assets acquired 1,046.6            
Goodwill $ 7,846.9            
IPG | Trade Names              
Liabilities Assumed [Abstract]              
Intangible assets, Gross Carrying Value   792.0   792.0      
IPG | Customer Relationships              
Liabilities Assumed [Abstract]              
Intangible assets, Gross Carrying Value   3,616.0   3,616.0      
IPG | Technology and Other              
Liabilities Assumed [Abstract]              
Intangible assets, Gross Carrying Value   $ 170.9   $ 170.9