Shareholdings
| Concept | As at 2024-03-31 | As at 2024-03-31 | As at 2024-03-31 | As at 2024-03-31 | As at 2024-03-31 | As at 2024-03-31 | As at 2024-03-31 | 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 | As at 2023-03-31 | As at 2023-03-31 | As at 2023-03-31 | 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 | 
                                                ㈱みずほフィナンシャルグループ
                                                
                                             | 
                                                ㈱森組
                                                
                                             | 
                                                ジオスター㈱
                                                
                                             | 
                                                高周波熱錬㈱
                                                
                                             | 
                                                太平洋セメント㈱
                                                
                                             | 
                                                阪和興業㈱
                                                
                                             | 
                                                日本コンクリート工業㈱
                                                
                                             | 
                                                大豊建設㈱
                                                
                                             | 
                                                不動テトラ㈱
                                                
                                             | 
                                                ㈱奥村組
                                                
                                             | 
                                                三井住友建設㈱
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | 
| Number of shares | 
                                                60,387
                                                
                                                    
                                                        xbrli:shares
                                                    
                                                
                                             | 
                                                
                                                
                                                    
                                                        xbrli:shares
                                                    
                                                
                                             | 
                                                
                                                
                                                    
                                                        xbrli:shares
                                                    
                                                
                                             | 
                                                122,300
                                                
                                                    
                                                        xbrli:shares
                                                    
                                                
                                             | 
                                                19,800
                                                
                                                    
                                                        xbrli:shares
                                                    
                                                
                                             | 
                                                30,600
                                                
                                                    
                                                        xbrli:shares
                                                    
                                                
                                             | 
                                                600,000
                                                
                                                    
                                                        xbrli:shares
                                                    
                                                
                                             | 
                                                
                                                
                                                    
                                                        xbrli:shares
                                                    
                                                
                                             | 
                                                
                                                
                                                    
                                                        xbrli:shares
                                                    
                                                
                                             | 
                                                
                                                
                                                    
                                                        xbrli:shares
                                                    
                                                
                                             | 
                                                332,800
                                                
                                                    
                                                        xbrli:shares
                                                    
                                                
                                             | 
                                                332,800
                                                
                                                    
                                                        xbrli:shares
                                                    
                                                
                                             | 
                                                10,000
                                                
                                                    
                                                        xbrli:shares
                                                    
                                                
                                             | 
                                                60,387
                                                
                                                    
                                                        xbrli:shares
                                                    
                                                
                                             | 
                                                37,000
                                                
                                                    
                                                        xbrli:shares
                                                    
                                                
                                             | 
                                                600,000
                                                
                                                    
                                                        xbrli:shares
                                                    
                                                
                                             | 
                                                30,600
                                                
                                                    
                                                        xbrli:shares
                                                    
                                                
                                             | 
                                                52
                                                
                                                    
                                                        xbrli:shares
                                                    
                                                
                                             | 
                                                1,100
                                                
                                                    
                                                        xbrli:shares
                                                    
                                                
                                             | 
                                                19,800
                                                
                                                    
                                                        xbrli:shares
                                                    
                                                
                                             | 
                                                556
                                                
                                                    
                                                        xbrli:shares
                                                    
                                                
                                             | 
                                                122,300
                                                
                                                    
                                                        xbrli:shares
                                                    
                                                
                                             | 
| Carrying amount | 
                                                183,938,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                136,976,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                69,676,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                181,458,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                243,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                143,104,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                127,795,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                2,910,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                113,406,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                136,160,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                153,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                120,717,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                84,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                325,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                49,242,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                1,740,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                84,998,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Purpose of shareholding, overview of business alliance, quantitative effects of shareholding and reason for increase in number of shares | 
                                                財務関係の関係強化、安定した資金調達のため。
                                                
                                             |  |  | 
                                                営業関係の関係強化、安定した資材調達及び技術交流のため。
                                                
                                             | 
                                                営業関係の関係強化、安定した資材調達及び技術交流のため。
                                                
                                             | 
                                                営業関係の関係強化、安定した資材調達のため。
                                                
                                             | 
                                                営業関係の関係強化、販路拡大のため。
                                                
                                             |  |  |  | 
                                                営業関係の関係強化、販路拡大及び技術交流のため。
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | 
| Whether issuer of aforementioned shares holds reporting company's shares | 
                                                無(注)2
                                                
                                             | 
                                                無
                                                
                                             | 
                                                無
                                                
                                             | 
                                                有
                                                
                                             | 
                                                有
                                                
                                             | 
                                                有
                                                
                                             | 
                                                有
                                                
                                             | 
                                                有
                                                
                                             | 
                                                無
                                                
                                             | 
                                                無
                                                
                                             | 
                                                有
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — |