Key Financial Data Of Reporting Company
| Concept | As at 2024-03-31 | As at 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 | 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 | 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 | ||||||||||||||||||||||||||||
| Operating revenue | — | — | — | 
                                                6,006,264,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                6,219,832,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | 
                                                7,069,962,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                7,307,192,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                6,517,474,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                6,734,830,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                4,471,124,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                4,723,455,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                4,927,131,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                5,156,697,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
| Ordinary profit (loss) | — | — | — | 
                                                953,351,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                995,087,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | 
                                                1,178,865,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                1,185,351,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                1,625,155,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                1,590,089,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                -272,660,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                -83,868,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                -242,859,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                -319,007,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
| Profit (loss) | — | — | — | 
                                                707,176,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | 
                                                810,017,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                1,245,864,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | 
                                                10,458,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                -336,299,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
| Share capital | — | — | — | — | — | — | — | — | 
                                                702,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | 
                                                702,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | 
                                                702,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                702,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                702,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Total number of issued shares | — | — | — | — | — | — | — | — | 
                                                1,932,000
                                                
                                                    
                                                        xbrli:shares
                                                    
                                                
                                             | — | — | — | — | 
                                                1,932,000
                                                
                                                    
                                                        xbrli:shares
                                                    
                                                
                                             | — | — | — | — | — | 
                                                1,932,000
                                                
                                                    
                                                        xbrli:shares
                                                    
                                                
                                             | — | — | — | 
                                                1,932,000
                                                
                                                    
                                                        xbrli:shares
                                                    
                                                
                                             | — | — | — | 
                                                1,932,000
                                                
                                                    
                                                        xbrli:shares
                                                    
                                                
                                             | 
| Net assets | — | — | — | — | — | — | — | 
                                                7,373,863,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                5,173,743,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | 
                                                4,453,723,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                6,632,448,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                5,890,425,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                3,715,322,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                4,627,515,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                2,428,131,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                4,579,483,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                2,309,650,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Total assets | — | — | — | — | — | — | — | 
                                                11,818,116,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                7,042,459,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | 
                                                6,803,157,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                11,050,309,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                12,182,536,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                7,070,250,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                10,853,968,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                5,539,717,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                11,730,867,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                4,544,702,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Net assets per share | — | — | — | — | — | — | — | 
                                                3,797.02
                                                
                                             | 
                                                2,680.32
                                                
                                             | — | — | — | — | 
                                                2,307.24
                                                
                                             | 
                                                3,354.20
                                                
                                             | — | — | — | 
                                                2,970.56
                                                
                                             | 
                                                1,924.67
                                                
                                             | 
                                                2,321.64
                                                
                                             | — | — | 
                                                1,257.86
                                                
                                             | — | 
                                                2,299.72
                                                
                                             | — | 
                                                1,196.44
                                                
                                             | 
| Dividend paid per share | — | — | — | 
                                                80
                                                
                                             | — | — | — | — | — | — | — | — | 
                                                80
                                                
                                             | — | — | — | 
                                                50
                                                
                                             | — | — | — | — |  | — | — |  | — | — | — | 
| Interim dividend paid per share | — | — | — |  | — | — | — | — | — | — | — | — |  | — | — | — |  | — | — | — | — |  | — | — |  | — | — | — | 
| Basic earnings (loss) per share | — | — | — | 
                                                366.36
                                                
                                             | — | — | 
                                                379.00
                                                
                                             | — | — | — | — | — | 
                                                419.62
                                                
                                             | — | — | 
                                                425.29
                                                
                                             | 
                                                645.40
                                                
                                             | 
                                                616.71
                                                
                                             | — | — | — | 
                                                5.42
                                                
                                             | 
                                                -43.40
                                                
                                             | — | 
                                                -174.21
                                                
                                             | — | 
                                                -366.30
                                                
                                             | — | 
| Diluted earnings per share | — | — | — |  | — | — |  | — | — | — | — | — |  | — | — |  |  |  | — | — | — |  |  | — |  | — |  | — | 
| Equity-to-asset ratio | — | — | — | — | — | — | — | 
                                                0.620
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.735
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | — | 
                                                0.655
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.586
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | 
                                                0.471
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.526
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.413
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                0.438
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                0.378
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                0.508
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
| Rate of return on equity | — | — | — | 
                                                0.147
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                0.106
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | — | — | 
                                                0.198
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                0.135
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.406
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.233
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | 
                                                0.004
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                -0.019
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                -0.132
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                -0.146
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
| Price-earnings ratio | — | — | — | 
                                                5.15
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                4.98
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | — | — | 
                                                3.50
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                3.46
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                2.62
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                2.75
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | 
                                                147.23
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                -18.39
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                -2.68
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                -1.27
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
| Payout ratio | — | — | — | 
                                                0.218
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | 
                                                0.191
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | 
                                                0.077
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | — | 
                                                
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | 
| Net cash provided by (used in) operating activities | — | — | — | — | — | — | 
                                                1,461,301,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | 
                                                1,170,297,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                2,878,063,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | 
                                                200,817,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                731,246,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
| Net cash provided by (used in) investing activities | — | — | — | — | — | — | 
                                                -490,376,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | 
                                                -524,125,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                -33,189,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | 
                                                197,266,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                -1,585,277,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
| Net cash provided by (used in) financing activities | — | — | — | — | — | — | 
                                                -90,331,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | 
                                                -1,718,147,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                -839,980,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | 
                                                -146,830,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                266,472,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
| Cash and cash equivalents | — | — | — | — | — | — | — | 
                                                2,528,061,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | 
                                                1,531,783,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                2,547,034,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                491,311,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | 
                                                251,862,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
| Number of employees | 
                                                11
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                11
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                10
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                2
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                60
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                23
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                39
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                10
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                19
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                59
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | 
                                                55
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                20
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                57
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                21
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                59
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                23
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
| Average number of temporary employees | 
                                                
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                1
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                1
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | 
                                                1
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                1
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                1
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                1
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                1
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                1
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
| Total shareholder return | — | — | — | — | — | — | — | — | 
                                                2.184
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | — | 
                                                1.667
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | — | — | 
                                                1.816
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | 
                                                0.831
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | 
                                                0.486
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
| Total return on share price index | — | — | — | — | — | — | — | — | 
                                                6.856
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | — | 
                                                4.820
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | — | — | 
                                                5.170
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | 
                                                1.892
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | 
                                                0.763
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             |