Key Financial Data Of Reporting Company
| Concept | 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 | 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 | — | — | — | — | — | — | — | — | 
                                                29,186,611,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                21,329,421,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                19,996,133,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                27,875,634,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                20,652,054,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                28,168,011,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                20,863,798,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                28,366,909,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                20,149,743,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                27,660,674,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
| Ordinary profit (loss) | — | — | — | — | — | — | — | — | 
                                                1,857,012,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                1,332,842,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                1,428,820,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                1,820,826,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                1,535,176,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                1,874,225,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                1,790,889,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                2,105,397,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                1,665,733,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                1,749,186,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
| Profit (loss) | — | — | — | — | — | — | — | — | — | — | — | 
                                                1,117,991,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                1,167,293,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                1,149,953,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                1,288,798,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | 
                                                1,246,194,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
| Share capital | — | — | — | — | — | — | — | — | — | 
                                                3,412,524,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | 
                                                3,412,524,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                3,412,524,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | 
                                                3,412,524,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                3,412,524,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Total number of issued shares | — | — | — | — | — | — | — | — | — | 
                                                7,864,000
                                                
                                                    
                                                        xbrli:shares
                                                    
                                                
                                             | — | — | — | — | — | 
                                                7,864,000
                                                
                                                    
                                                        xbrli:shares
                                                    
                                                
                                             | — | 
                                                39,324,000
                                                
                                                    
                                                        xbrli:shares
                                                    
                                                
                                             | — | — | — | — | — | 
                                                39,324,000
                                                
                                                    
                                                        xbrli:shares
                                                    
                                                
                                             | — | — | — | 
                                                39,324,000
                                                
                                                    
                                                        xbrli:shares
                                                    
                                                
                                             | 
| Net assets | — | — | — | — | — | — | 
                                                26,645,842,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                22,138,392,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | 
                                                25,197,432,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                21,161,189,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                19,648,604,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                23,239,013,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                22,173,194,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                18,851,112,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                21,150,794,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                18,046,781,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Total assets | — | — | — | — | — | — | 
                                                48,587,129,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                43,309,504,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | 
                                                47,534,946,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                42,580,638,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                41,162,713,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                45,832,606,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                43,248,010,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                38,642,534,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                42,892,152,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                38,393,048,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Net assets per share | — | — | — | — | — | — | 
                                                3,516.71
                                                
                                             | — | — | 
                                                2,909.22
                                                
                                             | — | — | — | — | 
                                                3,332.26
                                                
                                             | 
                                                2,786.39
                                                
                                             | — | 
                                                2,591.68
                                                
                                             | 
                                                3,078.59
                                                
                                             | — | — | — | 
                                                2,898.66
                                                
                                             | 
                                                2,453.84
                                                
                                             | 
                                                2,771.74
                                                
                                             | — | — | 
                                                2,354.84
                                                
                                             | 
| Dividend paid per share | — | — | — | — | — | — | — | — | — | — | — | 
                                                60.00
                                                
                                             | 
                                                33.00
                                                
                                             | — | — | — | 
                                                10.00
                                                
                                             | — | — | — | 
                                                9.50
                                                
                                             | — | — | — | — | 
                                                8.50
                                                
                                             | — | — | 
| Interim dividend paid per share | — | — | — | — | — | — | — | — | — | — | — | 
                                                30.00
                                                
                                             | 
                                                5.50
                                                
                                             | — | — | — | 
                                                5.00
                                                
                                             | — | — | — | 
                                                4.50
                                                
                                             | — | — | — | — | 
                                                4.00
                                                
                                             | — | — | 
| Basic earnings (loss) per share | — | — | — | — | — | — | — | — | 
                                                197.66
                                                
                                             | — | — | 
                                                147.14
                                                
                                             | 
                                                153.89
                                                
                                             | 
                                                181.38
                                                
                                             | — | — | 
                                                151.33
                                                
                                             | — | — | 
                                                178.51
                                                
                                             | 
                                                168.03
                                                
                                             | 
                                                188.95
                                                
                                             | — | — | — | 
                                                162.88
                                                
                                             | 
                                                155.79
                                                
                                             | — | 
| Diluted earnings per share | — | — | — | — | — | — | — | — |  | — | — |  |  |  | — | — |  | — | — |  |  |  | — | — | — |  |  | — | 
| Equity-to-asset ratio | — | — | — | — | — | — | 
                                                0.548
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                0.511
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | — | 
                                                0.530
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.497
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                0.477
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.507
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | 
                                                0.513
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.488
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.493
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                0.470
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
| Rate of return on equity | — | — | — | — | — | — | — | — | 
                                                0.058
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                0.052
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.057
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.057
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                0.060
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                0.059
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.070
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.067
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | 
                                                0.072
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.058
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
| Price-earnings ratio | — | — | — | — | — | — | — | — | 
                                                7.5
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                10.1
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                10.0
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                8.5
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                9.5
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                8.1
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                9.7
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                8.6
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | 
                                                10.6
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                11.1
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
| Payout ratio | — | — | — | — | — | — | — | — | — | — | — | 
                                                0.408
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.357
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | 
                                                0.330
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | 
                                                0.283
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | — | 
                                                0.261
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
| Net cash provided by (used in) operating activities | — | — | — | — | — | — | — | — | 
                                                3,243,225,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | 
                                                1,811,598,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | 
                                                2,651,107,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                2,829,106,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | 
                                                3,079,169,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
| Net cash provided by (used in) investing activities | — | — | — | — | — | — | — | — | 
                                                -2,011,233,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | 
                                                -3,075,905,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | 
                                                -3,362,892,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                -816,683,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | 
                                                -1,143,390,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
| Net cash provided by (used in) financing activities | — | — | — | — | — | — | — | — | 
                                                -1,442,377,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | 
                                                -508,706,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | 
                                                1,372,655,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                -783,145,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | 
                                                237,151,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
| Cash and cash equivalents | — | — | — | — | — | — | 
                                                6,346,666,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | 
                                                6,556,974,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                8,328,863,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                7,668,817,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                6,436,572,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
| Number of employees | 
                                                7
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                672
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                249
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                7
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                30
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                679
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                724
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                256
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                286
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                45
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | 
                                                729
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                291
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                297
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                733
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | 
                                                748
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                302
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                770
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                305
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
| Average number of temporary employees | 
                                                
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                615
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                11
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                2
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                615
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                620
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                11
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                13
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                5
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | 
                                                600
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                15
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                16
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                628
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | 
                                                681
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                22
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                711
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                27
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
| Total shareholder return | — | — | — | — | — | — | — | — | — | 
                                                1.002
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | — | — | 
                                                0.998
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                0.911
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | — | — | 
                                                0.989
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | 
                                                1.019
                                                
                                                    
                                                        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
                                                    
                                                
                                             |