Employees
| Concept | As at 2025-03-31 | As at 2025-03-31 | As at 2025-03-31 | 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 | 
                                                宇部フィルム㈱
                                                
                                             | 
                                                宇部エクシモ㈱
                                                
                                             | 
                                                UBEマシナリー㈱
                                                
                                             | 
                                                ㈱ティーユーエレクトロニクス
                                                
                                             | 
                                                ㈱福島製作所
                                                
                                             | 
                                                宇部物流サービス㈱
                                                
                                             | 
                                                ㈱宇部総合サービス
                                                
                                             | 
| Ratio of female employees in managerial positions | 
                                                0.021
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.057
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.020
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.045
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.043
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.076
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.133
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
| Ratio of male employees taking childcare leave | |||||||
| All employees | 
                                                1.000
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                1.500
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.667
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                1.000
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.250
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                1.000
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
| Differences in wages between male and female employees | |||||||
| All employees | 
                                                0.757
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.767
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.774
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.617
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.836
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.804
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.705
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
| Regular employees | 
                                                0.763
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.803
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.798
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.617
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.886
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.858
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.798
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
| Non-regular employees | 
                                                0.724
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.842
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.523
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.603
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                1.108
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.542
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.564
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             |