Shareholdings
| Concept | As at 2024-03-31 | As at 2024-03-31 | As at 2024-03-31 | As at 2024-03-31 | As at 2023-03-31 | As at 2023-03-31 | As at 2023-03-31 | As at 2023-03-31 | 
|---|---|---|---|---|---|---|---|---|
| Shareholdings | ||||||||
| Reporting company | ||||||||
| Details of specified investment shares held for purposes other than pure investment | ||||||||
| Issue | 
                                                日本金属㈱
                                                
                                             | 
                                                ㈱八十二銀行
                                                
                                             | 
                                                ㈱みずほフィナンシャルグループ
                                                
                                             | 
                                                大崎電気工業㈱
                                                
                                             | — | — | — | — | 
| Number of shares | 
                                                1,000
                                                
                                                    
                                                        xbrli:shares
                                                    
                                                
                                             | 
                                                
                                                
                                                    
                                                        xbrli:shares
                                                    
                                                
                                             | 
                                                18,323
                                                
                                                    
                                                        xbrli:shares
                                                    
                                                
                                             | 
                                                29,300
                                                
                                                    
                                                        xbrli:shares
                                                    
                                                
                                             | 
                                                26,598
                                                
                                                    
                                                        xbrli:shares
                                                    
                                                
                                             | 
                                                437,650
                                                
                                                    
                                                        xbrli:shares
                                                    
                                                
                                             | 
                                                1,000
                                                
                                                    
                                                        xbrli:shares
                                                    
                                                
                                             | 
                                                18,323
                                                
                                                    
                                                        xbrli:shares
                                                    
                                                
                                             | 
| Carrying amount | 
                                                859,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                55,811,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                20,011,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                14,150,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                251,648,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                956,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                34,410,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Purpose of shareholding, overview of business alliance, quantitative effects of shareholding and reason for increase in number of shares | 
                                                取引関係維持の強化
                                                
                                             | 
                                                取引関係維持の強化
                                                
                                             | 
                                                取引関係維持の強化
                                                
                                             | 
                                                取引関係維持の強化、持株会の定期購入
                                                
                                             | — | — | — | — | 
| Whether issuer of aforementioned shares holds reporting company's shares | 
                                                有
                                                
                                             | 
                                                無
                                                
                                             | 
                                                無
                                                
                                             | 
                                                無
                                                
                                             | — | — | — | — |