v3.26.1
Other Intangible Assets and Goodwill - Additional Information (Details) - EUR (€)
€ in Millions
 12 Months Ended
Dec. 31, 2025
Dec. 31, 2024
Jan. 31, 2025
Dec. 31, 2023
Disclosure of detailed information about intangible assets [line items]        
Growth rate used to extrapolate cash flow projections (as a percent) 1.50%      
Other intangible assets € 1,606.0 € 790.4    
Impairment loss recognised in profit or loss, intangible assets and goodwill   85.4    
Increase (decrease) in intangible assets 815.6      
Cumulative depreciation and impairment charges        
Disclosure of detailed information about intangible assets [line items]        
Other intangible assets (403.4) (254.0)   € (116.9)
Impairment loss recognised in profit or loss, intangible assets and goodwill 88.5 83.3    
Gross carrying amount        
Disclosure of detailed information about intangible assets [line items]        
Other intangible assets 2,009.4 1,044.4   921.0
Additions 573.8 115.2    
Miscellaneous | Gross carrying amount        
Disclosure of detailed information about intangible assets [line items]        
Additions   97.1    
In-process R&D        
Disclosure of detailed information about intangible assets [line items]        
Other intangible assets 473.3 485.5    
In-process R&D | Cumulative depreciation and impairment charges        
Disclosure of detailed information about intangible assets [line items]        
Other intangible assets (140.5) (55.1)   0.0
Impairment loss recognised in profit or loss, intangible assets and goodwill 85.4 55.1    
In-process R&D | Gross carrying amount        
Disclosure of detailed information about intangible assets [line items]        
Other intangible assets 613.8 € 540.6   € 443.5
Additions € 565.1      
Biotheus Inc.,        
Disclosure of detailed information about intangible assets [line items]        
Intangible assets     € 172.8  
Biotheus Inc., | Rights and Other Clinical Pipeline Candidates        
Disclosure of detailed information about intangible assets [line items]        
Intangible assets     € 167.7