v3.25.4
Income Tax - Additional Information (Detail) - EUR (€)
€ in Thousands
 12 Months Ended
Dec. 31, 2025
Dec. 31, 2024
Dec. 31, 2023
Dec. 31, 2022
Dec. 31, 2017
Income Tax [Line Items]          
Statutory tax rate 30.60% 30.20% 30.40%    
Corporate income tax rate 21.00% 21.00% 21.00%    
Remeasurement of deferred taxes resulted in tax income € 100        
Deferred tax liabilities 3,807 € 5,804      
Deferred tax liabilities deferred income adjustment € (2,000)        
Percentage on limitation on tax loss carryforwards after prior period 80.00%        
Percentage on limitation on tax loss carryforwards before prior period         100.00%
Current income tax € 9 7,790 € 0    
Profit (198,436) 21,346 (96,994)    
Accumulated tax losses, no deferred tax assets beyond offsetting amounts for deferred tax liabilities 493,500 301,700      
Current tax liabilities, current 2,318 2,008      
Prior period income tax refund from income tax prepayments 4,700        
Income tax paid 9,163 13,098 2,960    
Deferred tax assets 0 0      
Deferred tax liabilities 3,807 5,804      
Immatics Biotechnologies GmbH [Member]          
Income Tax [Line Items]          
Current income tax   0 7,800 € 0  
Immatics N V [Member]          
Income Tax [Line Items]          
Profit   € 0      
Immatics N V [Member] | Immatics N.V. [Member]          
Income Tax [Line Items]          
Profit 0   0    
Immatics N V, Immatics Biotechnologies GmbH and Immatics US Inc [Member]          
Income Tax [Line Items]          
Current income tax € 0   0    
Current tax liabilities, current     € 0    
GERMANY          
Income Tax [Line Items]          
Statutory tax rate 15.00%        
Corporate income tax rate 10.00% 70.00%      
Trade tax rate   60.00%      
CorporateTax | GERMANY | Immatics Biotechnologies GmbH [Member]          
Income Tax [Line Items]          
Percentage Of Pretax Income Subject To Income Tax   30.00%      
Trade Tax | GERMANY | Immatics Biotechnologies GmbH [Member]          
Income Tax [Line Items]          
Percentage Of Pretax Income Subject To Income Tax   40.00%      
Indefinite Tax Losses Carryforward [Member]          
Income Tax [Line Items]          
Tax effect of tax losses € 493,500 € 301,700      
Twenty Six Year Tax Losses Carryforward [Member]          
Income Tax [Line Items]          
Tax effect of tax losses € 26,000