Key Financial Data Of Group
| Concept | 2023-01-01 to 2023-12-31 | 2023-01-01 to 2023-12-31 | As at 2023-12-31 | As at 2023-12-31 | As at 2022-12-31 | 2022-01-01 to 2022-12-31 | 2022-01-01 to 2022-12-31 | As at 2022-12-31 | As at 2021-12-31 | As at 2021-12-31 | 2021-01-01 to 2021-12-31 | 2021-01-01 to 2021-12-31 | 2020-01-01 to 2020-12-31 | 2020-01-01 to 2020-12-31 | As at 2020-12-31 | As at 2020-12-31 | As at 2019-12-31 | 2019-01-01 to 2019-12-31 | 
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Key financial data of group | ||||||||||||||||||
| Business results of group | ||||||||||||||||||
| Net sales | 
                                                3,164,212,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                3,648,872,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                3,600,607,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                3,170,455,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                2,863,166,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                3,306,541,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                2,012,759,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                2,432,901,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                2,675,778,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Ordinary profit (loss) | 
                                                250,511,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                298,648,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                517,614,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                453,561,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                327,990,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                416,650,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                -361,327,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                -395,627,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                205,482,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Profit (loss) attributable to owners of parent | — | 
                                                75,878,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                418,991,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | 
                                                245,260,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                -299,041,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | 
| Comprehensive income | — | 
                                                -105,345,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                494,568,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | 
                                                300,414,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                -289,962,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | 
| Net assets | — | — | 
                                                2,942,024,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                2,822,380,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                2,873,409,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                2,817,970,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                1,616,801,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                1,643,217,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | 
                                                1,309,402,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                1,351,805,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                1,615,743,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
| Total assets | — | — | 
                                                4,305,462,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                4,086,871,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                4,399,922,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                4,192,453,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                2,995,661,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                3,121,427,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | 
                                                2,248,856,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                2,172,540,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                2,396,294,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
| Net assets per share | — | — | 
                                                1,267.61
                                                
                                             | 
                                                1,216.06
                                                
                                             | 
                                                1,310.62
                                                
                                             | — | — | 
                                                1,285.34
                                                
                                             | 
                                                927.91
                                                
                                             | 
                                                943.07
                                                
                                             | — | — | — | — | 
                                                766.18
                                                
                                             | 
                                                790.99
                                                
                                             | 
                                                1,890.86
                                                
                                             | — | 
| Basic earnings (loss) per share | 
                                                9.98
                                                
                                             | 
                                                32.87
                                                
                                             | — | — | — | 
                                                238.61
                                                
                                             | 
                                                203.75
                                                
                                             | — | — | — | 
                                                86.97
                                                
                                             | 
                                                142.10
                                                
                                             | 
                                                -140.26
                                                
                                             | 
                                                -174.98
                                                
                                             | — | — | — | 
                                                247.20
                                                
                                             | 
| Diluted earnings per share |  |  | — | — | — |  |  | — | — | — |  |  |  |  | — | — | — |  | 
| Equity-to-asset ratio | — | — | 
                                                0.683
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.691
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.653
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                0.672
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.540
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.526
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | — | 
                                                0.582
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.622
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.674
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
| Rate of return on equity | 
                                                0.008
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.026
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | 
                                                0.186
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.161
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | 
                                                0.101
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.166
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | 
                                                0.144
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
| Price-earnings ratio | 
                                                167.4
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                50.8
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | 
                                                7.8
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                9.1
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | 
                                                
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | 
                                                
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
| Net cash provided by (used in) operating activities | — | 
                                                63,021,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                470,246,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | 
                                                957,440,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                -131,883,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | 
| Net cash provided by (used in) investing activities | — | 
                                                -61,779,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                -55,042,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | 
                                                -62,115,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                -57,172,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | 
| Net cash provided by (used in) financing activities | — | 
                                                122,983,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                708,501,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | 
                                                33,109,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                -26,797,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | 
| Cash and cash equivalents | — | — | 
                                                3,403,321,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                3,260,933,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | 
                                                2,146,734,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | 
                                                1,207,179,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
| Number of employees | — | — | 
                                                158
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                142
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                147
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                135
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                130
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                145
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | — | 
                                                167
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                145
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                160
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
| Average number of temporary employees | — | — | 
                                                12
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                12
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                12
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                12
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                10
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                11
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | — | 
                                                8
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                7
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                7
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — |