Key Financial Data Of Reporting Company
| Concept | 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 | 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 reporting company | |||||||||||||||||||||||||
| Business results of reporting company | |||||||||||||||||||||||||
| Net sales | — | — | — | 
                                                296,682,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                565,358,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | 
                                                552,825,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                310,514,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                497,213,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                284,167,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                226,324,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                393,647,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                343,764,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                184,998,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
| Ordinary profit (loss) | — | — | — | 
                                                79,219,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                102,117,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | 
                                                86,047,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                90,637,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                51,035,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                40,109,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                35,603,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                55,909,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                30,887,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                18,374,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
| Profit (loss) | — | — | — | 
                                                65,253,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | 
                                                81,932,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | 
                                                39,286,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                22,813,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | 
                                                2,204,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
| Share capital | — | — | 
                                                55,935,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | 
                                                55,935,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                55,935,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                55,935,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                55,935,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
| Total number of issued shares | — | — | 
                                                154,111,000
                                                
                                                    
                                                        xbrli:shares
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | 
                                                154,111,000
                                                
                                                    
                                                        xbrli:shares
                                                    
                                                
                                             | — | — | 
                                                154,111,000
                                                
                                                    
                                                        xbrli:shares
                                                    
                                                
                                             | — | — | 
                                                154,111,000
                                                
                                                    
                                                        xbrli:shares
                                                    
                                                
                                             | — | — | — | 
                                                154,111,000
                                                
                                                    
                                                        xbrli:shares
                                                    
                                                
                                             | — | — | 
| Net assets | — | — | 
                                                287,198,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | 
                                                472,552,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                395,199,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                247,058,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                320,915,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                181,420,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                168,684,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                280,155,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                145,469,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                222,694,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Total assets | — | — | 
                                                430,684,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | 
                                                722,666,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                645,480,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                402,583,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                598,889,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                375,187,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                345,005,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                531,229,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                296,308,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                445,579,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Net assets per share | — | — | 
                                                1,865.24
                                                
                                             | — | — | — | — | — | 
                                                3,069.02
                                                
                                             | — | 
                                                2,566.76
                                                
                                             | — | 
                                                1,604.60
                                                
                                             | 
                                                2,083.00
                                                
                                             | — | 
                                                1,178.42
                                                
                                             | — | — | 
                                                1,095.79
                                                
                                             | 
                                                1,818.60
                                                
                                             | — | — | 
                                                945.02
                                                
                                             | — | 
                                                1,434.23
                                                
                                             | 
| Dividend paid per share | — | — | — | 
                                                120.00
                                                
                                             | — | — | — | — | — | — | — | 
                                                100.00
                                                
                                             | — | — | — | — | 
                                                80.00
                                                
                                             | 
                                                76.00
                                                
                                             | — | — | — | — | — | 
                                                45.00
                                                
                                             | — | 
| Interim dividend paid per share | — | — | — | 
                                                50.00
                                                
                                             | — | — | — | — | — | — | — | 
                                                20.00
                                                
                                             | — | — | — | — | 
                                                30.00
                                                
                                             | 
                                                20.00
                                                
                                             | — | — | — | — | — | 
                                                20.00
                                                
                                             | — | 
| Basic earnings (loss) per share | — | — | — | 
                                                423.79
                                                
                                             | 
                                                485.86
                                                
                                             | — | — | — | — | 
                                                469.42
                                                
                                             | — | 
                                                532.15
                                                
                                             | — | — | 
                                                311.51
                                                
                                             | — | 
                                                255.19
                                                
                                             | 
                                                148.20
                                                
                                             | — | — | 
                                                268.62
                                                
                                             | 
                                                75.89
                                                
                                             | — | 
                                                14.32
                                                
                                             | — | 
| Diluted earnings per share | — | — | — |  |  | — | — | — | — |  | — |  | — | — |  | — |  |  | — | — |  |  | — |  | — | 
| Equity-to-asset ratio | — | — | 
                                                0.6668
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | — | — | 
                                                0.6539
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                0.6123
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                0.6137
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.5350
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                0.4835
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                0.4889
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.5270
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                0.4909
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                0.4955
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
| Rate of return on equity | — | — | — | 
                                                0.2443
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.1724
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | — | 
                                                0.2019
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                0.3824
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                0.1597
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                0.2244
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.1452
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                0.1652
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.0527
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                0.0148
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
| Price-earnings ratio | — | — | — | 
                                                5.77
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                5.03
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | — | 
                                                5.03
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                4.43
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                4.81
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                5.87
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                12.11
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                6.68
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                20.66
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                109.47
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
| Payout ratio | — | — | — | 
                                                0.2832
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | — | — | — | — | 
                                                0.1879
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | — | 
                                                0.3135
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.5128
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | — | — | 
                                                3.1417
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
| Net cash provided by (used in) operating activities | — | — | — | — | 
                                                67,059,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | 
                                                86,503,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | 
                                                15,172,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | 
                                                34,465,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                53,796,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
| Net cash provided by (used in) investing activities | — | — | — | — | 
                                                -15,214,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | 
                                                -14,661,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | 
                                                -16,712,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | 
                                                -37,538,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                -27,856,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
| Net cash provided by (used in) financing activities | — | — | — | — | 
                                                -23,077,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | 
                                                -62,894,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | 
                                                -16,231,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | 
                                                11,697,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                -12,638,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
| Cash and cash equivalents | — | — | — | — | — | — | — | — | 
                                                86,333,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                52,798,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                41,600,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | 
                                                53,592,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | 
                                                36,303,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Number of employees | 
                                                12
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                368
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                3,705
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                10,030
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                3,337
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                368
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                10,410
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                10,395
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                3,672
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                10,574
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                3,674
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                3,694
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                10,324
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                3,725
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                11,258
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
| Average number of temporary employees | 
                                                32
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                69
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                486
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                741
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                417
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                69
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                842
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                872
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                506
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                1,170
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                525
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                513
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                1,200
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                550
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                1,168
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
| Total shareholder return | — | — | 
                                                1.820
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | 
                                                1.690
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                1.078
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                1.216
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | 
                                                1.024
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
| Total return on share price index | — | — | 
                                                1.8246
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | 
                                                1.5148
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                1.1810
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                1.2107
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | 
                                                1.0739
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — |