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 | 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 | — | — | 
                                                
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                18,867,885,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | 
                                                12,551,933,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                15,246,170,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                7,876,877,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                8,890,439,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                6,738,154,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                7,509,942,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                5,678,650,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                6,382,727,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
| Operating revenue | — | — | 
                                                1,384,769,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | 
                                                
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | 
                                                
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
| Ordinary profit (loss) | — | — | 
                                                236,615,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                6,265,098,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | 
                                                3,984,910,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                4,246,452,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                1,904,450,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                1,932,172,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                969,678,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                1,588,856,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                607,769,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                1,023,639,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
| Profit (loss) | — | — | 
                                                -239,436,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | 
                                                2,883,807,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                1,690,919,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | 
                                                668,914,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                546,571,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
| Share capital | — | — | — | — | — | — | — | — | — | — | — | 
                                                4,978,566,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                4,978,566,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | 
                                                4,978,566,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                4,978,566,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                4,978,566,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Total number of issued shares | — | — | — | — | — | — | — | — | — | — | — | 
                                                11,961,100
                                                
                                                    
                                                        xbrli:shares
                                                    
                                                
                                             | — | — | — | 
                                                11,961,100
                                                
                                                    
                                                        xbrli:shares
                                                    
                                                
                                             | — | — | — | — | — | 
                                                11,961,100
                                                
                                                    
                                                        xbrli:shares
                                                    
                                                
                                             | — | — | — | 
                                                11,961,100
                                                
                                                    
                                                        xbrli:shares
                                                    
                                                
                                             | — | — | — | 
                                                11,961,100
                                                
                                                    
                                                        xbrli:shares
                                                    
                                                
                                             | 
| Net assets | — | — | — | — | — | 
                                                17,735,761,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | 
                                                11,456,878,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                12,647,701,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                14,334,361,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                11,872,879,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                10,396,842,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                10,386,194,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                9,122,490,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                9,111,720,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                8,374,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Total assets | — | — | — | — | — | 
                                                25,828,326,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | 
                                                14,525,641,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                17,653,800,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                19,605,292,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                16,353,010,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                14,324,609,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                12,561,465,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                11,181,761,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                11,007,647,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                10,148,548,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Net assets per share | — | — | — | — | — | 
                                                1,508.08
                                                
                                             | — | — | — | — | — | 
                                                974.18
                                                
                                             | — | — | — | 
                                                1,075.44
                                                
                                             | 
                                                1,218.86
                                                
                                             | — | — | — | 
                                                1,009.55
                                                
                                             | 
                                                884.05
                                                
                                             | 
                                                883.14
                                                
                                             | — | — | 
                                                775.69
                                                
                                             | — | 
                                                774.77
                                                
                                             | — | 
                                                712.04
                                                
                                             | 
| Dividend paid per share | — | — | 
                                                90.0
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | 
                                                80.0
                                                
                                             | — | — | — | 
                                                40.0
                                                
                                             | — | — | — | — | 
                                                30.0
                                                
                                             | — | — | 
                                                20.0
                                                
                                             | — | — | — | 
| Interim dividend paid per share | — | — | 
                                                40.0
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | 
                                                30.0
                                                
                                             | — | — | — | 
                                                15.0
                                                
                                             | — | — | — | — | 
                                                10.0
                                                
                                             | — | — | 
                                                10.0
                                                
                                             | — | — | — | 
| Basic earnings (loss) per share | — | — | 
                                                -20.36
                                                
                                             | — | 
                                                327.49
                                                
                                             | — | — | — | — | — | — | — | — | — | 
                                                245.21
                                                
                                             | — | — | 
                                                255.25
                                                
                                             | 
                                                143.78
                                                
                                             | 
                                                140.11
                                                
                                             | — | — | — | 
                                                56.88
                                                
                                             | 
                                                94.10
                                                
                                             | — | 
                                                46.47
                                                
                                             | — | 
                                                70.66
                                                
                                             | — | 
| Diluted earnings per share | — | — |  | — |  | — | — | — | — | — | — | — | — | — |  | — | — |  |  |  | — | — | — |  |  | — |  | — |  | — | 
| Equity-to-asset ratio | — | — | — | — | — | 
                                                0.687
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | — | — | 
                                                0.789
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | 
                                                0.716
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.731
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | 
                                                0.726
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.726
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.827
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                0.816
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                0.828
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                0.825
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
| Rate of return on equity | — | — | 
                                                -0.020
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                0.240
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | 
                                                0.250
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                0.229
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.173
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.148
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | 
                                                0.076
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.114
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                0.065
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                0.092
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
| Price-earnings ratio | — | — | 
                                                
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                16.3
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | 
                                                9.8
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                9.9
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                9.2
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                9.4
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | 
                                                31.6
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                19.1
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                32.6
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                21.5
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
| Payout ratio | — | — | 
                                                
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | 
                                                0.326
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | 
                                                0.278
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | — | 
                                                0.527
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                0.430
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | 
| Net cash provided by (used in) operating activities | — | — | — | — | 
                                                3,281,993,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | — | 
                                                3,113,333,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                1,406,563,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | 
                                                1,607,756,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                840,144,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
| Net cash provided by (used in) investing activities | — | — | — | — | 
                                                -194,810,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | — | 
                                                -788,096,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                -2,100,942,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | 
                                                -321,061,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                -117,820,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
| Net cash provided by (used in) financing activities | — | — | — | — | 
                                                -213,343,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | — | 
                                                -773,990,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                832,588,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | 
                                                -236,173,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                -411,623,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
| Cash and cash equivalents | — | — | — | — | — | 
                                                9,373,250,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | 
                                                6,096,888,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                4,458,349,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                4,089,982,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | 
                                                2,862,740,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
| Number of employees | 
                                                93
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                49
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                310
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                51
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                210
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                159
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                49
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                7
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                215
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                293
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | 
                                                273
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                197
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                203
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                178
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                188
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                165
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
| Average number of temporary employees | 
                                                14
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                14
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                146
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                28
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                131
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                103
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                14
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                1
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                120
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                120
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | 
                                                76
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                76
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                64
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                64
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                66
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                66
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
| Total shareholder return | — | — | — | — | — | — | — | — | — | — | — | 
                                                3.904
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | 
                                                1.878
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | — | — | 
                                                0.983
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | 
                                                1.291
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | 
                                                1.073
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
| Total return on share price index | — | — | — | — | — | — | — | — | — | — | — | 
                                                1.962
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | 
                                                1.388
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | — | — | 
                                                1.312
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | 
                                                1.286
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | 
                                                0.905
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             |