v3.26.1
Shareholders' equity - Additional Information (Detail) - EUR (€)
€ / shares in Units, € in Millions
12 Months Ended
Jan. 23, 2025
Dec. 04, 2023
May 31, 2021
Nov. 30, 2016
Dec. 31, 2025
Dec. 31, 2024
Aug. 27, 2025
Jan. 01, 2025
Aug. 27, 2024
Jan. 30, 2024
Dec. 31, 2023
Shareholders equity [Line Items]                      
Subscribed capital         € 696 € 696          
Number of shares issued         557,186,400 557,186,400         557,186,400
Shares have no par value         true true          
Percentage of dividend paid for one share         40.00%            
Buyback of shares         23,952,416            
Weighted average share price         € 5.22            
Shares buyback related cost         € 150            
Number of shares represented by FDRs         2,558,176            
Amount of deeply subordinated fixed rate resettable securities 1       € 550 € 550            
Percentage of deeply subordinated fixed rate resettable securities of first call     2.875% 5.625%              
Percentage of deeply subordinated fixed rate resettable securities of nominal value     99.409% 99.304%              
Amount of tender premium and transaction cost     € 26 € 8              
Amount of issued notice for redemption deeply subordinated fixed rate resettable securities 1   € 550                  
Amount of deeply subordinated fixed rate resettable securities 2     € 625   625            
Payments in respect of deeply subordinated fixed rate resettable securities occurred             € 15 € 1 € 18 € 31  
Tax on perpetual bonds coupon accrual         4 € 6         € 14
Amount of repurchased for securities € 63         37          
Issue of deeply subordinated fixed rate resettable securities 625         625          
Amount of cash outflow for repurchased of securities 59         35          
Gain in repurchased of securities 4         2          
Outstanding principal balance of securities         € 525            
Percenatge of statutory net profit on legal reserve         5.00%            
Percentage of issue of share capital         10.00%            
Legal reserve         € 70 70          
Net worth tax reserve         € 54 54          
Percenage of distributed reserve in accordance with luxembourg law requirement         20.00%            
Amount Of Repurchased For Securities 63         37          
Issue Of Deeply Subordinated Fixed Rate Resettable Securities 625         625          
Amount Of Cash Outflow For Repurchased Of Securities 59         35          
Gain In Repurchased Of Securities € 4         € 2          
Shareholder [Member]                      
Shareholders equity [Line Items]                      
Percentage of voting equity interests acquired         20.00%            
Chairman [Member] | Top of range [member]                      
Shareholders equity [Line Items]                      
Percentage of voting equity interests acquired         50.00%            
Chairman [Member] | Bottom of range [member]                      
Shareholders equity [Line Items]                      
Percentage of voting equity interests acquired         33.00%            
Class A Ordinary Shares [Member]                      
Shareholders equity [Line Items]                      
Number of shares issued         371,457,600 371,457,600         371,457,600
Class B Ordinary Shares [Member]                      
Shareholders equity [Line Items]                      
Number of shares issued         185,728,800 185,728,800         185,728,800
Buyback of shares         11,976,209            
Weighted average share price         € 2.09            
Treasury shares [member]                      
Shareholders equity [Line Items]                      
Other reserves         € 181 € 198