Key Financial Data Of Reporting Company
| Concept | As at 2024-03-31 | As at 2024-03-31 | As at 2024-03-31 | As at 2024-03-31 | As at 2024-03-31 | As at 2024-03-31 | As at 2024-03-31 | 2023-04-01 to 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 | 2022-04-01 to 2023-03-31 | As at 2023-03-31 | As at 2023-03-31 | 2022-04-01 to 2023-03-31 | 2021-04-01 to 2022-03-31 | 2021-04-01 to 2022-03-31 | As at 2022-03-31 | As at 2022-03-31 | As at 2021-03-31 | 2020-04-01 to 2021-03-31 | 2020-04-01 to 2021-03-31 | As at 2021-03-31 | 2019-04-01 to 2020-03-31 | As at 2020-03-31 | 2019-04-01 to 2020-03-31 | As at 2020-03-31 | 
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Key financial data of reporting company | |||||||||||||||||||||||||||||
| Business results of reporting company | |||||||||||||||||||||||||||||
| Net sales | — | — | — | — | — | — | — | 
                                                10,963,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                13,332,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | 
                                                11,005,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                13,389,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                10,420,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                12,866,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                10,476,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                12,878,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                10,344,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                12,992,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
| Ordinary profit (loss) | — | — | — | — | — | — | — | 
                                                234,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                282,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | 
                                                310,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                311,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                83,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                142,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                88,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                144,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                59,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                88,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
| Profit (loss) | — | — | — | — | — | — | — | 
                                                185,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | 
                                                197,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                109,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | 
                                                104,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                80,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
| Share capital | — | — | — | — | — | — | — | — | — | — | — | 
                                                1,710,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                1,710,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | 
                                                1,710,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                1,710,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                1,710,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Total number of issued shares | — | — | — | — | — | — | — | — | — | — | — | 
                                                3,420,000
                                                
                                                    
                                                        xbrli:shares
                                                    
                                                
                                             | — | — | 
                                                3,420,000
                                                
                                                    
                                                        xbrli:shares
                                                    
                                                
                                             | — | — | — | — | — | 
                                                3,420,000
                                                
                                                    
                                                        xbrli:shares
                                                    
                                                
                                             | — | — | — | 
                                                3,420,000
                                                
                                                    
                                                        xbrli:shares
                                                    
                                                
                                             | — | — | — | 
                                                3,420,000
                                                
                                                    
                                                        xbrli:shares
                                                    
                                                
                                             | 
| Net assets | — | — | — | — | — | — | — | — | — | 
                                                5,553,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                4,640,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                4,129,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                4,952,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                4,734,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                3,909,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                4,755,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                3,989,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                4,428,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                3,724,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Total assets | — | — | — | — | — | — | — | — | — | 
                                                13,362,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                10,876,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                9,650,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                12,085,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                11,761,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                9,225,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                11,479,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                8,800,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                11,082,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                8,432,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Net assets per share | — | — | — | — | — | — | — | — | — | 
                                                1,563.31
                                                
                                             | — | 
                                                1,415.93
                                                
                                             | — | — | 
                                                1,260.25
                                                
                                             | 
                                                1,392.43
                                                
                                             | — | — | — | 
                                                1,324.82
                                                
                                             | 
                                                1,192.98
                                                
                                             | 
                                                1,339.76
                                                
                                             | — | — | 
                                                1,217.38
                                                
                                             | — | 
                                                1,241.06
                                                
                                             | — | 
                                                1,129.45
                                                
                                             | 
| Dividend paid per share | — | — | — | — | — | — | — | 
                                                18
                                                
                                             | — | — | — | — | — | 
                                                15
                                                
                                             | — | — | — | 
                                                15
                                                
                                             | — | — | — | — | 
                                                15
                                                
                                             | — | — | 
                                                15
                                                
                                             | — | — | — | 
| Interim dividend paid per share | — | — | — | — | — | — | — |  | — | — | — | — | — |  | — | — | — |  | — | — | — | — |  | — | — |  | — | — | — | 
| Basic earnings (loss) per share | — | — | — | — | — | — | — | 
                                                56.57
                                                
                                             | 
                                                63.46
                                                
                                             | — | — | — | — | 
                                                60.20
                                                
                                             | — | — | 
                                                61.31
                                                
                                             | 
                                                33.42
                                                
                                             | 
                                                40.84
                                                
                                             | — | — | — | 
                                                31.95
                                                
                                             | 
                                                38.16
                                                
                                             | — | 
                                                23.69
                                                
                                             | — | 
                                                26.85
                                                
                                             | — | 
| Diluted earnings per share | — | — | — | — | — | — | — |  |  | — | — | — | — |  | — | — |  |  |  | — | — | — |  |  | — |  | — |  | — | 
| Equity-to-asset ratio | — | — | — | — | — | — | — | — | — | 
                                                0.3801
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                0.4266
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                0.4279
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.3743
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | 
                                                0.3660
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.4238
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.3792
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                0.4533
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                0.3661
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                0.4417
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
| Rate of return on equity | — | — | — | — | — | — | — | 
                                                0.0423
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.0429
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | — | 
                                                0.0491
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                0.0451
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.0277
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.0307
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | 
                                                0.0272
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.0296
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                0.0215
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                0.0222
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
| Price-earnings ratio | — | — | — | — | — | — | — | 
                                                11.05
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                9.85
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | — | 
                                                10.85
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                10.65
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                18.25
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                14.93
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | 
                                                26.61
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                23.95
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                15.41
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                13.59
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
| Payout ratio | — | — | — | — | — | — | — | 
                                                0.3182
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | — | — | 
                                                0.2492
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | 
                                                0.4489
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | — | 
                                                0.4695
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                0.6332
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | 
| Net cash provided by (used in) operating activities | — | — | — | — | — | — | — | — | 
                                                289,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | 
                                                -81,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                309,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | 
                                                489,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                389,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
| Net cash provided by (used in) investing activities | — | — | — | — | — | — | — | — | 
                                                -192,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | 
                                                -254,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                -145,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | 
                                                -336,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                -311,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
| Net cash provided by (used in) financing activities | — | — | — | — | — | — | — | — | 
                                                -66,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | 
                                                263,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                -138,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | 
                                                -309,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                -129,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
| Cash and cash equivalents | — | — | — | — | — | — | — | — | — | 
                                                299,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | 
                                                269,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                341,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                316,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | 
                                                473,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
| Number of employees | 
                                                27
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                99
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                43
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                27
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                176
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                23
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                43
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                379
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                23
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                269
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                187
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                276
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                384
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | 
                                                391
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                283
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                398
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                285
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                395
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                278
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
| Total shareholder return | — | — | — | — | — | — | — | — | — | — | — | 
                                                1.28
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                1.30
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | — | — | 
                                                1.19
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | 
                                                1.71
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | 
                                                0.70
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
| Total return on share price index | — | — | — | — | — | — | — | — | — | — | — | 
                                                1.96
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                1.39
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | — | — | 
                                                1.31
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | 
                                                1.29
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | 
                                                0.90
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             |