Employees
| Concept | As at 2025-03-31 | As at 2025-03-31 | As at 2025-03-31 | As at 2025-03-31 | 
|---|---|---|---|---|
| Employees | ||||
| Metrics related to human capital diversity | ||||
| Metrics of consolidated subsidiaries | ||||
| Consolidated subsidiaries | 
                                                中銀証券株式会社
                                                
                                             | 
                                                株式会社CBS
                                                
                                             | 
                                                株式会社中国銀行
                                                
                                             | 
                                                中銀事務センター株式会社
                                                
                                             | 
| Ratio of female employees in managerial positions | 
                                                
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.090
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
| Ratio of male employees taking childcare leave | ||||
| All employees | 
                                                
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.987
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
| Differences in wages between male and female employees | ||||
| All employees | 
                                                0.808
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.817
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.485
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.792
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
| Regular employees | 
                                                0.733
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.860
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.525
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.772
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
| Non-regular employees | 
                                                0.796
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.724
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.705
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.544
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             |