Key Financial Data Of Reporting Company
| Concept | As at 2024-03-31 | As at 2024-03-31 | 2023-04-01 to 2024-03-31 | As at 2024-03-31 | 2023-04-01 to 2024-03-31 | As at 2024-03-31 | As at 2024-03-31 | As at 2024-03-31 | As at 2024-03-31 | As at 2024-03-31 | As at 2024-03-31 | 2022-04-01 to 2023-03-31 | As at 2023-03-31 | As at 2023-03-31 | 2022-04-01 to 2023-03-31 | 2021-04-01 to 2022-03-31 | 2021-04-01 to 2022-03-31 | As at 2022-03-31 | As at 2022-03-31 | As at 2021-03-31 | 2020-04-01 to 2021-03-31 | 2020-04-01 to 2021-03-31 | As at 2021-03-31 | 2019-04-01 to 2020-03-31 | As at 2020-03-31 | 2019-04-01 to 2020-03-31 | As at 2020-03-31 | 
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Key financial data of reporting company | |||||||||||||||||||||||||||
| Business results of reporting company | |||||||||||||||||||||||||||
| Net sales | — | — | 
                                                5,972,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                192,992,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | 
                                                6,075,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                176,922,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                6,225,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                168,525,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                5,765,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                163,556,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                11,239,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                132,642,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
| Ordinary profit (loss) | — | — | 
                                                2,690,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                7,318,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | 
                                                2,964,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                6,813,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                2,834,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                7,877,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                2,244,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                7,306,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                7,745,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                5,995,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
| Profit (loss) | — | — | 
                                                2,592,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | 
                                                1,366,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                3,035,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | 
                                                1,627,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                6,425,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
| Share capital | — | — | — | — | — | — | — | — | — | — | 
                                                1,785,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                1,785,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | 
                                                1,785,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                1,785,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                1,785,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Total number of issued shares | — | — | — | — | — | — | — | — | — | — | 
                                                44,063,000
                                                
                                                    
                                                        xbrli:shares
                                                    
                                                
                                             | — | 
                                                44,063,000
                                                
                                                    
                                                        xbrli:shares
                                                    
                                                
                                             | — | — | — | — | — | 
                                                44,063,000
                                                
                                                    
                                                        xbrli:shares
                                                    
                                                
                                             | — | — | — | 
                                                22,031,000
                                                
                                                    
                                                        xbrli:shares
                                                    
                                                
                                             | — | — | — | 
                                                26,672,000
                                                
                                                    
                                                        xbrli:shares
                                                    
                                                
                                             | 
| Net assets | — | — | — | — | — | 
                                                29,973,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | 
                                                10,372,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                9,688,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                26,757,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                24,747,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                9,950,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                21,263,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                8,664,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                22,018,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                12,764,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Total assets | — | — | — | — | — | 
                                                61,872,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | 
                                                22,960,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                22,338,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                57,202,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                54,145,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                23,828,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                51,391,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                23,020,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                47,886,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                25,888,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Net assets per share | — | — | — | — | — | 
                                                680.23
                                                
                                             | — | — | — | — | 
                                                235.39
                                                
                                             | — | 
                                                219.88
                                                
                                             | 
                                                607.25
                                                
                                             | — | — | — | 
                                                558.17
                                                
                                             | 
                                                225.83
                                                
                                             | 
                                                478.92
                                                
                                             | — | — | 
                                                196.64
                                                
                                             | — | 
                                                453.67
                                                
                                             | — | 
                                                263.50
                                                
                                             | 
| Dividend paid per share | — | — | 
                                                40.0
                                                
                                             | — | — | — | — | — | — | — | — | 
                                                38.0
                                                
                                             | — | — | — | 
                                                54.0
                                                
                                             | — | — | — | — | 
                                                66.0
                                                
                                             | — | — | 
                                                66.5
                                                
                                             | — | — | — | 
| Interim dividend paid per share | — | — | 
                                                20.0
                                                
                                             | — | — | — | — | — | — | — | — | 
                                                19.0
                                                
                                             | — | — | — | 
                                                35.0
                                                
                                             | — | — | — | — | 
                                                25.0
                                                
                                             | — | — | 
                                                43.0
                                                
                                             | — | — | — | 
| Basic earnings (loss) per share | — | — | 
                                                58.85
                                                
                                             | — | 
                                                117.46
                                                
                                             | — | — | — | — | — | — | 
                                                31.01
                                                
                                             | — | — | 
                                                86.78
                                                
                                             | 
                                                68.88
                                                
                                             | 
                                                119.28
                                                
                                             | — | — | — | 
                                                35.46
                                                
                                             | 
                                                105.82
                                                
                                             | — | 
                                                132.65
                                                
                                             | — | 
                                                72.73
                                                
                                             | — | 
| Diluted earnings per share | — | — |  | — |  | — | — | — | — | — | — |  | — | — |  |  |  | — | — | — |  |  | — |  | — |  | — | 
| Equity-to-asset ratio | — | — | — | — | — | 
                                                0.484
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | — | 
                                                0.452
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                0.434
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.468
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | 
                                                0.454
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.418
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.411
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                0.376
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                0.459
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                0.493
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
| Rate of return on equity | — | — | 
                                                0.2585
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                0.1825
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | — | — | — | 
                                                0.1391
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                0.1489
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.3261
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.2300
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | 
                                                0.1519
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.2254
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                0.6406
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                0.1700
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
| Price-earnings ratio | — | — | 
                                                24.50
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                12.28
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | — | — | — | 
                                                46.63
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                16.66
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                24.01
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                13.87
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | 
                                                37.21
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                12.47
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                8.74
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                15.95
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
| Payout ratio | — | — | 
                                                0.680
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | 
                                                1.225
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | 
                                                0.530
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | — | 
                                                0.930
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                0.170
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | 
| Net cash provided by (used in) operating activities | — | — | — | — | 
                                                7,392,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | 
                                                3,959,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                5,633,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | 
                                                9,314,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                5,057,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
| Net cash provided by (used in) investing activities | — | — | — | — | 
                                                -4,002,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | 
                                                -3,308,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                -3,245,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | 
                                                -2,974,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                -2,615,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
| Net cash provided by (used in) financing activities | — | — | — | — | 
                                                -1,944,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | 
                                                -1,996,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                -1,618,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | 
                                                -6,555,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                -506,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
| Cash and cash equivalents | — | — | — | — | — | 
                                                17,133,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | 
                                                15,683,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                17,028,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                16,254,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | 
                                                16,465,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
| Number of employees | 
                                                61
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                61
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                232
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                2,080
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                255
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                1,787
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                1,199
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                333
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                61
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                57
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                2,023
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | 
                                                2,054
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                53
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                1,962
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                52
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                1,737
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                51
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
| Average number of temporary employees | 
                                                50
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                50
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                1,142
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                5,591
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                3,756
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                4,399
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                369
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                274
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                50
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                48
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                5,399
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | 
                                                5,667
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                46
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                5,670
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                43
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                3,713
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                42
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
| Total shareholder return | — | — | — | — | — | — | — | — | — | — | 
                                                2.765
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                2.703
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | — | — | 
                                                2.995
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | 
                                                2.358
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | 
                                                2.028
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
| Total return on share price index | — | — | — | — | — | — | — | — | — | — | 
                                                1.739
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                1.259
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | — | — | 
                                                1.223
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | 
                                                1.228
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | 
                                                0.882
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             |