Key Financial Data Of Group
| Concept | As at 2024-03-31 | 2023-04-01 to 2024-03-31 | As at 2023-03-31 | 2022-04-01 to 2023-03-31 | As at 2022-03-31 | 2021-04-01 to 2022-03-31 | 2020-04-01 to 2021-03-31 | As at 2021-03-31 | As at 2020-03-31 | 2019-04-01 to 2020-03-31 | 
|---|---|---|---|---|---|---|---|---|---|---|
| Key financial data of group | ||||||||||
| Business results of group | ||||||||||
| Net sales | — | 
                                                5,056,464,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                4,923,246,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                4,614,725,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                4,257,859,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                4,609,421,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Ordinary profit (loss) | — | 
                                                928,505,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                853,968,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                777,906,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                653,622,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                616,172,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Net assets | 
                                                6,266,287,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                5,669,839,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                5,200,131,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                4,659,510,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                4,381,469,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
| Total assets | 
                                                8,590,984,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                8,115,854,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                7,571,515,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                6,962,332,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                6,744,633,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
| Net assets per share | 
                                                1,486.43
                                                
                                             | — | 
                                                1,358.35
                                                
                                             | — | 
                                                1,245.93
                                                
                                             | — | — | 
                                                1,138.21
                                                
                                             | 
                                                1,047.77
                                                
                                             | — | 
| Basic earnings (loss) per share | — | 
                                                152.26
                                                
                                             | — | 
                                                136.13
                                                
                                             | — | 
                                                126.39
                                                
                                             | 
                                                100.63
                                                
                                             | — | — | 
                                                97.09
                                                
                                             | 
| Diluted earnings per share | — |  | — |  | — |  |  | — | — |  | 
| Equity-to-asset ratio | 
                                                0.729
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                0.699
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                0.687
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                0.669
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.650
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
| Rate of return on equity | — | 
                                                0.107
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                0.105
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                0.104
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.092
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                0.099
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
| Price-earnings ratio | — | 
                                                7.86
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                7.65
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                7.95
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                10.15
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                9.41
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
| Net cash provided by (used in) operating activities | — | 
                                                430,578,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                544,510,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                604,363,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                591,249,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                678,181,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Net cash provided by (used in) investing activities | — | 
                                                -72,828,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                -10,328,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                -141,187,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                -117,163,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                -52,203,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Net cash provided by (used in) financing activities | — | 
                                                -203,726,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                -191,136,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                -31,255,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                -194,611,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                385,760,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Cash and cash equivalents | 
                                                2,833,883,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                2,679,848,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                2,336,787,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                1,903,770,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                1,624,245,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
| Number of employees | 
                                                146
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                144
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                149
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                154
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                163
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
| Average number of temporary employees | 
                                                
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — |