Key Financial Data Of Reporting Company
| Concept | As at 2025-03-31 | As at 2025-03-31 | 2024-04-01 to 2025-03-31 | As at 2025-03-31 | As at 2025-03-31 | As at 2025-03-31 | As at 2025-03-31 | As at 2025-03-31 | As at 2025-03-31 | As at 2025-03-31 | As at 2025-03-31 | As at 2025-03-31 | 2024-04-01 to 2025-03-31 | 2023-04-01 to 2024-03-31 | 2023-04-01 to 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 | 
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Key financial data of reporting company | |||||||||||||||||||||||||||||
| Business results of reporting company | |||||||||||||||||||||||||||||
| Operating revenue | — | — | 
                                                18,824,835,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | 
                                                8,659,721,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                8,146,069,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                17,543,417,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                8,504,663,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                16,249,195,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                8,654,786,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                16,727,466,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                8,173,634,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                16,071,021,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
| Ordinary profit (loss) | — | — | 
                                                935,308,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | 
                                                549,062,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                299,577,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                588,079,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                604,919,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                802,429,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                535,315,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                814,203,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                420,356,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                623,561,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
| Profit (loss) | — | — | — | — | — | — | — | — | — | — | — | — | 
                                                208,175,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                287,479,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                482,572,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                369,410,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | 
                                                298,994,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
| Share capital | — | — | — | — | 
                                                1,262,736,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | 
                                                1,262,736,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                1,262,736,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | 
                                                1,262,736,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                1,262,736,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Total number of issued shares | — | — | — | — | 
                                                5,651,000
                                                
                                                    
                                                        xbrli:shares
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | 
                                                5,651,000
                                                
                                                    
                                                        xbrli:shares
                                                    
                                                
                                             | — | 
                                                5,651,000
                                                
                                                    
                                                        xbrli:shares
                                                    
                                                
                                             | — | — | — | — | — | 
                                                5,651,000
                                                
                                                    
                                                        xbrli:shares
                                                    
                                                
                                             | — | — | — | 
                                                5,651,000
                                                
                                                    
                                                        xbrli:shares
                                                    
                                                
                                             | 
| Net assets | — | 
                                                6,123,975,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                4,596,946,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | 
                                                5,760,651,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                4,491,004,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                4,225,291,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                5,399,003,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                5,012,119,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                3,886,020,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                4,652,185,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                3,661,837,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Total assets | — | 
                                                18,836,671,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                13,987,571,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | 
                                                18,029,245,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                13,666,283,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                13,653,246,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                17,548,215,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                17,539,372,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                13,633,156,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                18,173,010,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                14,014,921,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Net assets per share | — | 
                                                1,184.18
                                                
                                             | — | — | 
                                                921.07
                                                
                                             | — | — | — | — | — | — | — | — | — | — | 
                                                1,103.24
                                                
                                             | 
                                                900.86
                                                
                                             | — | 
                                                841.30
                                                
                                             | 
                                                1,034.01
                                                
                                             | — | — | — | 
                                                943.44
                                                
                                             | 
                                                761.58
                                                
                                             | 
                                                863.72
                                                
                                             | — | — | 
                                                706.79
                                                
                                             | 
| Dividend paid per share | — | — | — | — | — | — | — | — | — | — | — | — | 
                                                15.00
                                                
                                             | 
                                                15.00
                                                
                                             | — | — | — | 
                                                15.00
                                                
                                             | — | — | — | 
                                                15.00
                                                
                                             | — | — | — | — | 
                                                15.00
                                                
                                             | — | — | 
| Interim dividend paid per share | — | — | — | — | — | — | — | — | — | — | — | — | 
                                                7.5
                                                
                                             | 
                                                7.5
                                                
                                             | — | — | — | 
                                                7.5
                                                
                                             | — | — | — | 
                                                7.5
                                                
                                             | — | — | — | — | 
                                                5
                                                
                                             | — | — | 
| Basic earnings (loss) per share | — | — | 
                                                101.65
                                                
                                             | — | — | — | — | — | — | — | — | — | 
                                                41.79
                                                
                                             | 
                                                57.44
                                                
                                             | 
                                                76.70
                                                
                                             | — | — | 
                                                95.19
                                                
                                             | — | — | 
                                                102.99
                                                
                                             | 
                                                71.72
                                                
                                             | 
                                                95.05
                                                
                                             | — | — | — | 
                                                57.07
                                                
                                             | 
                                                67.81
                                                
                                             | — | 
| Diluted earnings per share | — | — |  | — | — | — | — | — | — | — | — | — |  |  |  | — | — |  | — | — |  | 
                                                71.61
                                                
                                             | 
                                                94.91
                                                
                                             | — | — | — | 
                                                56.84
                                                
                                             | 
                                                67.54
                                                
                                             | — | 
| Equity-to-asset ratio | — | 
                                                0.313
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                0.327
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | 
                                                0.305
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.329
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                0.309
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.296
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | 
                                                0.274
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.285
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.246
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                0.261
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
| Rate of return on equity | — | — | 
                                                0.089
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | 
                                                0.046
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.066
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.072
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                0.119
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                0.104
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.098
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.106
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | 
                                                0.085
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.082
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
| Price-earnings ratio | — | — | 
                                                10.0
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | 
                                                24.2
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                15.1
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                11.3
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                8.3
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                7.6
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                10.9
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                8.2
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | 
                                                13.9
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                11.7
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
| Payout ratio | — | — | — | — | — | — | — | — | — | — | — | — | 
                                                0.359
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.261
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | 
                                                0.158
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | 
                                                0.209
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | — | 
                                                0.263
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
| Net cash provided by (used in) operating activities | — | — | 
                                                1,475,450,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | 
                                                565,686,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | 
                                                935,943,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                1,049,032,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | 
                                                1,124,484,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
| Net cash provided by (used in) investing activities | — | — | 
                                                -417,790,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | 
                                                -620,688,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | 
                                                -474,844,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                -188,017,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | 
                                                141,043,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
| Net cash provided by (used in) financing activities | — | — | 
                                                -255,639,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | 
                                                -417,625,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | 
                                                -683,863,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                -1,017,320,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | 
                                                -780,457,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
| Cash and cash equivalents | — | 
                                                2,906,008,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | — | — | 
                                                2,104,229,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                2,559,882,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                2,782,369,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                2,938,341,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
| Number of employees | 
                                                21
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                449
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                157
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                270
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                161
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                103
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                161
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                88
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                5
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                21
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                2
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | 
                                                448
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                277
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                261
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                422
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | 
                                                430
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                262
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                425
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                265
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
| Average number of temporary employees | 
                                                7
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                152
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                18
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                133
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                92
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                34
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                92
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                34
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                1
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                7
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | 
                                                174
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                152
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                154
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                179
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | 
                                                190
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                164
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                189
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                166
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
| Total shareholder return | — | — | — | — | 
                                                1.700
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | 
                                                1.447
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                1.305
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | — | — | 
                                                1.270
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | 
                                                1.267
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
| Total return on share price index | — | — | — | — | 
                                                2.134
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | 
                                                2.168
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                1.534
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | — | — | 
                                                1.450
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | 
                                                1.421
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             |