v3.26.1
Financial instruments - Derivative and non-derivative financial instruments (Details)
€ in Thousands, $ in Thousands
 1 Months Ended 3 Months Ended 12 Months Ended
Aug. 31, 2025
Sep. 30, 2025
EUR (€)
Sep. 30, 2025
USD ($)
Apr. 30, 2024
item
Mar. 31, 2026
EUR (€)
Mar. 31, 2025
EUR (€)
Dec. 31, 2025
EUR (€)
Dec. 31, 2025
USD ($)
Reconciliation of derivatives embedded                
Distributions to noncontrolling interests         € 78,246 € 64,409    
Transactions with noncontrolling interests without loss of control         (8,152) (673)    
Put option liabilities         (23,828) 55,904    
Income tax expense         42,753 61,045    
Reconciliation of changes in fair value measurement                
Assets at beginning of period         31,002,333      
Assets at end of period         31,467,593 32,735,034 € 31,002,333  
Liabilities at beginning of period         16,719,524      
Liabilities at end of period         17,262,895   € 16,719,524  
InterWell Health LLC                
Reconciliation of derivatives embedded                
Ownership percentage 75.00%           92.00% 92.00%
Noncontrolling interests                
Reconciliation of derivatives embedded                
Transactions with noncontrolling interests without loss of control         (9,893) (1,853)    
Additional paid-in capital                
Reconciliation of derivatives embedded                
Transactions with noncontrolling interests without loss of control         1,741 1,180    
Retained earnings                
Reconciliation of derivatives embedded                
Put option liabilities         (23,828) 55,904    
Shareholders of Interwell Health                
Reconciliation of derivatives embedded                
Settlement of put options held by non-physician investors   € 311,614 $ 363,272          
Distributions to noncontrolling interests             € 311,614  
Increase (decrease) in put option liabilities             (312,941)  
Income tax expense             (34,679) $ (38,792)
Shareholders of Interwell Health | Noncontrolling interests                
Reconciliation of derivatives embedded                
Transactions with noncontrolling interests without loss of control             (76,201)  
Shareholders of Interwell Health | Additional paid-in capital                
Reconciliation of derivatives embedded                
Transactions with noncontrolling interests without loss of control             (235,413)  
Shareholders of Interwell Health | Retained earnings                
Reconciliation of derivatives embedded                
Put option liabilities             312,941  
Maximum                
Financial instruments                
Term of virtual power purchase agreement       15 years        
Germany                
Financial instruments                
Number of wind and solar energy project developers who signed contracts with company | item       2        
United States                
Financial instruments                
Number of wind and solar energy project developers who signed contracts with company | item       1        
Derivatives embedded in vPPAs | Fair Value | Level 3                
Reconciliation of derivatives embedded                
Opening balance net assets (liabilities) January 1,         (1,733) (25,394) (25,394)  
Settlements         2,660   10,867  
Gain (loss) recognized in profit or loss         (2,673)   11,308  
Foreign currency translation and other changes         99   1,486  
Closing balance net assets (liabilities) December 31,         € (1,647)   € (1,733)  
Derivatives embedded in vPPAs | Fair Value | Level 3 | Expected electricity prices                
Financial instruments                
Increase in input         10.00%   10.00% 10.00%
Decrease in input         10.00%   10.00% 10.00%
Sensitivity of derivatives embedded in vPPAs to increase in input         € 25,318   € 24,356  
Sensitivity of derivatives embedded in vPPAs to decrease in input         € (25,264)   € (24,305)  
Derivatives embedded in vPPAs | Fair Value | Level 3 | Expected production volumes                
Financial instruments                
Increase in input         10.00%   10.00% 10.00%
Decrease in input         10.00%   10.00% 10.00%
Sensitivity of derivatives embedded in vPPAs to increase in input         € (165)   € 155  
Sensitivity of derivatives embedded in vPPAs to decrease in input         € 165   € (155)  
Derivatives embedded in vPPAs | Fair Value | Level 3 | Expected interest rates                
Financial instruments                
Increase in input         1.00%   1.00% 1.00%
Decrease in input         1.00%   1.00% 1.00%
Sensitivity of derivatives embedded in vPPAs to increase in input         € (213)   € (183)  
Sensitivity of derivatives embedded in vPPAs to decrease in input         225   196  
Equity investments | Fair Value | Level 3                
Reconciliation of changes in fair value measurement                
Assets at beginning of period         13,771 29,154 29,154  
Increase         2,439   2,002  
Gain / loss recognized in profit or loss         (824)   (14,487)  
Foreign currency translation and other changes         331   (2,898)  
Assets at end of period         15,717   13,771  
Other financial assets measured at FVPL | Fair Value | Level 3                
Reconciliation of changes in fair value measurement                
Assets at beginning of period         99,154 142,264 142,264  
Increase             7,808  
Decrease             (22,855)  
Gain / loss recognized in profit or loss         3,418   (13,460)  
Foreign currency translation and other changes         2,225   (14,603)  
Assets at end of period         104,797   99,154  
Variable payments outstanding for acquisitions | Fair Value | Level 3                
Reconciliation of changes in fair value measurement                
Liabilities at beginning of period         3,262 7,933 7,933  
Increase         2,219   1,507  
Decrease         (87)   (4,581)  
Gain / loss recognized in profit or loss             (928)  
Foreign currency translation and other changes         109   (669)  
Liabilities at end of period         5,503   3,262  
Put option liabilities | Fair Value | Level 3                
Reconciliation of changes in fair value measurement                
Liabilities at beginning of period         793,043 € 1,299,117 1,299,117  
Increase         2,865   32,307  
Decrease         (6,696)   (341,992)  
Gain / loss recognized in equity         27,659   (54,964)  
Foreign currency translation and other changes         17,224   (141,425)  
Liabilities at end of period         € 834,095   € 793,043  
Put option liabilities | Fair Value | Level 3 | Assumed earnings or enterprise value                
Reconciliation of derivatives embedded                
Increase in input, liabilities         10.00%      
Increase (decrease) in fair value due to increase in input, liabilities         € 66,055      
Put option liabilities | Fair Value | Level 3 | Assumed earnings or enterprise value | Maximum                
Reconciliation of derivatives embedded                
Increase in fair value due to increase in input, as percentage of total liabilities         1.00%      
Increase in fair value due to increase in input, as percentage of equity         1.00%