Key Financial Data Of Group
| Concept | As at 2024-12-31 | As at 2024-12-31 | As at 2024-12-31 | As at 2024-12-31 | As at 2024-12-31 | As at 2024-12-31 | As at 2024-12-31 | As at 2024-12-31 | As at 2024-12-31 | 2024-01-01 to 2024-12-31 | 2024-01-01 to 2024-12-31 | As at 2024-12-31 | As at 2024-12-31 | As at 2024-12-31 | 2023-01-01 to 2023-12-31 | As at 2023-12-31 | 2023-01-01 to 2023-12-31 | As at 2023-12-31 | As at 2022-12-31 | 2022-01-01 to 2022-12-31 | As at 2022-12-31 | 2022-01-01 to 2022-12-31 | 2021-01-01 to 2021-12-31 | As at 2021-12-31 | As at 2021-12-31 | 2021-01-01 to 2021-12-31 | 2020-01-01 to 2020-12-31 | As at 2020-12-31 | 2020-01-01 to 2020-12-31 | As at 2020-12-31 | 
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Key financial data of group | ||||||||||||||||||||||||||||||
| Business results of group | ||||||||||||||||||||||||||||||
| Net sales | — | — | — | — | — | — | — | — | — | 
                                                5,903,921,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                5,901,003,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                5,713,249,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                5,716,297,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                5,281,174,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                5,284,030,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                5,544,946,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                5,541,932,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                5,014,103,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                5,017,286,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
| Ordinary profit (loss) | — | — | — | — | — | — | — | — | — | 
                                                563,199,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                572,420,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                553,833,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                529,916,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                173,779,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                171,539,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                464,089,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                480,187,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                400,361,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                390,571,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
| Profit (loss) attributable to owners of parent | — | — | — | — | — | — | — | — | — | — | 
                                                433,582,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                375,181,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | 
                                                181,369,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | 
                                                332,473,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                263,511,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
| Comprehensive income | — | — | — | — | — | — | — | — | — | — | 
                                                463,021,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                404,906,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | 
                                                188,160,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | 
                                                351,764,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                262,430,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
| Net assets | — | — | — | — | — | — | 
                                                4,228,757,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | 
                                                4,353,340,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                4,006,546,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                3,888,675,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                3,715,250,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                3,614,890,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                3,635,709,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                3,535,881,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                3,250,751,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                3,339,528,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Total assets | — | — | — | — | — | — | 
                                                6,091,979,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | 
                                                6,205,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                5,878,633,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                5,787,567,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                5,443,768,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                5,367,721,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                5,516,795,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                5,440,219,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                5,309,319,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                5,373,932,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Net assets per share | — | — | — | — | — | — | 
                                                2,687.43
                                                
                                             | — | — | — | — | — | 
                                                2,722.25
                                                
                                             | — | — | 
                                                2,430.17
                                                
                                             | — | 
                                                2,398.45
                                                
                                             | 
                                                2,189.34
                                                
                                             | — | 
                                                2,163.79
                                                
                                             | — | — | 
                                                2,087.41
                                                
                                             | 
                                                2,062.66
                                                
                                             | — | — | 
                                                1,893.73
                                                
                                             | — | 
                                                1,915.22
                                                
                                             | 
| Basic earnings (loss) per share | — | — | — | — | — | — | — | — | — | 
                                                268.08
                                                
                                             | 
                                                270.17
                                                
                                             | — | — | — | 
                                                230.76
                                                
                                             | — | 
                                                225.37
                                                
                                             | — | — | 
                                                106.27
                                                
                                             | — | 
                                                106.12
                                                
                                             | 
                                                190.53
                                                
                                             | — | — | 
                                                193.75
                                                
                                             | 
                                                150.13
                                                
                                             | — | 
                                                148.33
                                                
                                             | — | 
| Diluted earnings per share | — | — | — | — | — | — | — | — | — |  |  | — | — | — |  | — |  | — | — |  | — |  |  | — | — |  |  | — |  | — | 
| Equity-to-asset ratio | — | — | — | — | — | — | 
                                                0.694
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | — | — | 
                                                0.690
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                0.670
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                0.672
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.672
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                0.673
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                0.649
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.650
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                0.612
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                0.612
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
| Rate of return on equity | — | — | — | — | — | — | — | — | — | 
                                                0.106
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.105
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | 
                                                0.099
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                0.098
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                0.050
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                0.051
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.096
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                0.097
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.082
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                0.082
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
| Price-earnings ratio | — | — | — | — | — | — | — | — | — | 
                                                5.6
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                5.5
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | 
                                                6.3
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                6.5
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                12.1
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                12.2
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                6.8
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                6.7
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                7.5
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                7.6
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
| Net cash provided by (used in) operating activities | — | — | — | — | — | — | — | — | — | — | 
                                                329,332,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                378,639,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | 
                                                -30,528,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | 
                                                84,773,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                448,581,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
| Net cash provided by (used in) investing activities | — | — | — | — | — | — | — | — | — | — | 
                                                -22,666,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                -501,197,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | 
                                                -138,875,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | 
                                                -24,943,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                -63,358,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
| Net cash provided by (used in) financing activities | — | — | — | — | — | — | — | — | — | — | 
                                                -116,181,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                -113,576,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | 
                                                -108,672,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | 
                                                -55,816,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                -115,276,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
| Cash and cash equivalents | — | — | — | — | — | — | — | — | — | — | — | — | 
                                                1,170,233,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                979,748,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                1,215,883,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | 
                                                1,493,960,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | 
                                                1,489,946,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Number of employees | 
                                                78
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                103
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                6
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                78
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                83
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                270
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                94
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                6
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                281
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                103
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                274
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                265
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                265
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                256
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                270
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                261
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                255
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                264
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
| Average number of temporary employees | 
                                                16
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                12
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                16
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                10
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                38
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                10
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                38
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                12
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                35
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                34
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                34
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                34
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                36
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                36
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                38
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                38
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             |