Key Financial Data Of Reporting Company
| Concept | 2023-04-01 to 2024-03-31 | As at 2024-03-31 | 2023-04-01 to 2024-03-31 | As at 2024-03-31 | As at 2024-03-31 | As at 2024-03-31 | As at 2024-03-31 | As at 2024-03-31 | 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 | As at 2022-03-31 | 2021-04-01 to 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 | 
                                                8,469,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | 
                                                8,320,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                8,966,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | 
                                                8,115,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                8,820,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
| Ordinary income | — | — | 
                                                182,058,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | 
                                                148,759,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                135,711,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                143,132,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                154,698,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
| Ordinary profit (loss) | 
                                                7,506,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                30,868,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | 
                                                7,444,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                25,048,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                8,271,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                23,545,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                5,635,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                17,500,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                6,370,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                19,410,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
| Profit (loss) | 
                                                7,992,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | 
                                                7,401,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                8,292,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | 
                                                5,564,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                6,306,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
| Share capital | — | — | — | — | — | 
                                                30,000,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                30,000,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | 
                                                30,000,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                30,000,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                30,000,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Total number of issued shares | — | — | — | — | — | 
                                                45,942,000
                                                
                                                    
                                                        xbrli:shares
                                                    
                                                
                                             | — | — | — | 
                                                45,942,000
                                                
                                                    
                                                        xbrli:shares
                                                    
                                                
                                             | — | — | — | — | — | 
                                                45,942,000
                                                
                                                    
                                                        xbrli:shares
                                                    
                                                
                                             | — | — | — | 
                                                45,942,000
                                                
                                                    
                                                        xbrli:shares
                                                    
                                                
                                             | — | — | — | 
                                                45,942,000
                                                
                                                    
                                                        xbrli:shares
                                                    
                                                
                                             | 
| Net assets | — | — | — | 
                                                499,376,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                321,160,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                323,632,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                415,423,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                433,505,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                323,227,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                453,845,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                321,933,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                406,453,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                321,715,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Total assets | — | — | — | 
                                                11,137,853,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                325,444,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                325,026,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                10,517,951,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                10,670,304,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                324,519,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                9,706,533,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                322,242,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                8,966,437,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                322,082,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Net assets per share | — | — | — | 
                                                11,401.36
                                                
                                             | — | 
                                                7,332.76
                                                
                                             | — | — | — | 
                                                7,202.63
                                                
                                             | 
                                                9,245.50
                                                
                                             | — | — | 
                                                9,436.72
                                                
                                             | — | 
                                                7,118.99
                                                
                                             | 
                                                9,510.00
                                                
                                             | — | — | 
                                                7,028.28
                                                
                                             | — | 
                                                8,502.89
                                                
                                             | — | 
                                                7,031.36
                                                
                                             | 
| Dividend paid per share | 
                                                145
                                                
                                             | — | — | — | — | — | — | — | 
                                                120
                                                
                                             | — | — | — | 
                                                120
                                                
                                             | — | — | — | — | 
                                                120
                                                
                                             | — | — | 
                                                120
                                                
                                             | — | — | — | 
| Interim dividend paid per share | 
                                                70
                                                
                                             | — | — | — | — | — | — | — | 
                                                60
                                                
                                             | — | — | — | 
                                                60
                                                
                                             | — | — | — | — | 
                                                60
                                                
                                             | — | — | 
                                                60
                                                
                                             | — | — | — | 
| Basic earnings (loss) per share | 
                                                178.95
                                                
                                             | — | 
                                                474.71
                                                
                                             | — | — | — | — | — | 
                                                163.19
                                                
                                             | — | — | 
                                                391.79
                                                
                                             | 
                                                181.99
                                                
                                             | — | 
                                                332.40
                                                
                                             | — | — | 
                                                121.79
                                                
                                             | 
                                                236.28
                                                
                                             | — | 
                                                138.18
                                                
                                             | — | 
                                                282.17
                                                
                                             | — | 
| Diluted earnings per share |  | — |  | — | — | — | — | — |  | — | — |  | 
                                                181.54
                                                
                                             | — | 
                                                331.58
                                                
                                             | — | — | 
                                                121.13
                                                
                                             | 
                                                235.00
                                                
                                             | — | 
                                                137.52
                                                
                                             | — | 
                                                280.81
                                                
                                             | — | 
| Equity-to-asset ratio | — | — | — | 
                                                0.0448
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                0.9868
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | 
                                                0.9957
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.0394
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                0.0401
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                0.9960
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.0447
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                0.9968
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                0.0432
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                0.9964
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
| Rate of return on equity | 
                                                0.0247
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                0.0463
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | — | — | 
                                                0.0228
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                0.0421
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.0257
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                0.0350
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                0.0173
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.0262
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                0.0196
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                0.0322
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
| Price-earnings ratio | 
                                                24.92
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                9.39
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | — | — | 
                                                17.70
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                7.37
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                13.76
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                7.53
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                21.43
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                11.04
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                17.10
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                8.37
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
| Payout ratio | 
                                                0.8102
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | — | — | — | — | 
                                                0.7353
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | 
                                                0.6593
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | — | 
                                                0.9852
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                0.8683
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | 
| Net cash provided by (used in) operating activities | — | — | 
                                                294,419,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | 
                                                -338,479,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                797,685,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                903,597,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                22,883,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
| Net cash provided by (used in) investing activities | — | — | 
                                                -90,170,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | 
                                                -380,777,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                -85,510,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                -78,519,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                111,069,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
| Net cash provided by (used in) financing activities | — | — | 
                                                -10,509,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | 
                                                -8,049,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                -8,942,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                -5,495,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                -5,348,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
| Cash and cash equivalents | — | — | — | 
                                                2,223,711,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | 
                                                2,029,972,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                2,757,277,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                2,054,043,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | 
                                                1,234,458,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
| Number of employees | — | 
                                                306
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                3,549
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                65
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                9
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                199
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                2,979
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                9
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                3,463
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                3,591
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                9
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                3,774
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                3
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                3,829
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                7
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
| Average number of temporary employees | — | 
                                                49
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                626
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                17
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                6
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                554
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                669
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                724
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                1,186
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                1,409
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
| Total shareholder return | — | — | — | — | — | 
                                                1.627
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | 
                                                1.078
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | — | — | 
                                                0.916
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | 
                                                0.912
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | 
                                                0.794
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
| Total return on share price index | — | — | — | — | — | 
                                                1.961
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | 
                                                1.388
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | — | — | 
                                                1.311
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | 
                                                1.286
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | 
                                                0.904
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             |