Key Financial Data Of Reporting Company
| Concept | 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 | 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 | — | — | 
                                                94,243,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                102,885,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                95,486,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                103,261,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                102,439,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                110,179,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                95,334,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                102,995,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                94,837,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                101,799,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
| Ordinary profit (loss) | — | — | 
                                                5,355,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                6,037,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                8,971,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                9,085,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                13,539,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                14,799,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                11,626,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                12,260,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                7,984,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                9,154,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
| Profit (loss) | — | — | 
                                                4,671,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                7,250,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                10,441,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | 
                                                8,984,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                4,464,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
| Share capital | — | — | — | — | — | 
                                                7,229,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                7,229,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | 
                                                7,229,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                7,229,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                7,229,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Total number of issued shares | — | — | — | — | — | 
                                                37,470,000
                                                
                                                    
                                                        xbrli:shares
                                                    
                                                
                                             | — | 
                                                38,500,000
                                                
                                                    
                                                        xbrli:shares
                                                    
                                                
                                             | — | — | — | — | — | 
                                                40,160,000
                                                
                                                    
                                                        xbrli:shares
                                                    
                                                
                                             | — | — | — | 
                                                40,630,000
                                                
                                                    
                                                        xbrli:shares
                                                    
                                                
                                             | — | — | — | 
                                                40,630,000
                                                
                                                    
                                                        xbrli:shares
                                                    
                                                
                                             | 
| Net assets | — | — | — | — | 
                                                127,967,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                126,336,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                125,109,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                126,775,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                128,646,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                126,385,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                126,974,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                124,894,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                120,665,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                118,226,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Total assets | — | — | — | — | 
                                                158,800,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                152,166,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                152,386,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                158,831,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                163,139,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                156,837,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                161,791,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                155,605,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                157,488,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                147,964,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Net assets per share | — | — | — | — | 
                                                3,609.64
                                                
                                             | 
                                                3,563.63
                                                
                                             | — | 
                                                3,424.59
                                                
                                             | 
                                                3,470.18
                                                
                                             | — | — | — | 
                                                3,424.21
                                                
                                             | 
                                                3,364.03
                                                
                                             | 
                                                3,317.92
                                                
                                             | — | — | 
                                                3,263.57
                                                
                                             | — | 
                                                3,113.69
                                                
                                             | — | 
                                                3,050.75
                                                
                                             | 
| Dividend paid per share | — | — | 
                                                80.00
                                                
                                             | — | — | — | 
                                                80.00
                                                
                                             | — | — | — | 
                                                90.00
                                                
                                             | — | — | — | — | 
                                                90.00
                                                
                                             | — | — | 
                                                80.00
                                                
                                             | — | — | — | 
| Interim dividend paid per share | — | — | 
                                                40.00
                                                
                                             | — | — | — | 
                                                40.00
                                                
                                             | — | — | — | 
                                                40.00
                                                
                                             | — | — | — | — | 
                                                40.00
                                                
                                             | — | — | 
                                                40.00
                                                
                                             | — | — | — | 
| Basic earnings (loss) per share | — | — | 
                                                130.27
                                                
                                             | 
                                                126.80
                                                
                                             | — | — | 
                                                195.10
                                                
                                             | — | — | 
                                                178.93
                                                
                                             | 
                                                274.03
                                                
                                             | 
                                                277.39
                                                
                                             | — | — | — | 
                                                232.56
                                                
                                             | 
                                                222.29
                                                
                                             | — | 
                                                114.13
                                                
                                             | — | 
                                                117.56
                                                
                                             | — | 
| Diluted earnings per share | — | — |  |  | — | — |  | — | — |  |  |  | — | — | — |  |  | — |  | — |  | — | 
| Equity-to-asset ratio | — | — | — | — | 
                                                0.806
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.830
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                0.821
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.798
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | 
                                                0.789
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.806
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.785
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                0.803
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                0.766
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                0.799
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
| Rate of return on equity | — | — | 
                                                0.037
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.036
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                0.058
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                0.052
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.083
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.083
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | 
                                                0.074
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.069
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                0.037
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                0.037
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
| Price-earnings ratio | — | — | 
                                                24.7
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                25.4
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                17.1
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                18.7
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                13.6
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                13.5
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | 
                                                18.4
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                19.3
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                36.5
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                35.5
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
| Payout ratio | — | — | 
                                                0.614
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | 
                                                0.410
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | 
                                                0.328
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | — | 
                                                0.387
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                0.701
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | 
| Net cash provided by (used in) operating activities | — | — | — | 
                                                -7,480,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | 
                                                7,297,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                7,459,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | 
                                                9,198,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                9,347,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
| Net cash provided by (used in) investing activities | — | — | — | 
                                                74,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | 
                                                -2,949,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                -2,007,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | 
                                                -880,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                -1,760,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
| Net cash provided by (used in) financing activities | — | — | — | 
                                                -6,393,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | 
                                                -6,884,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                -5,956,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | 
                                                -5,112,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                -5,328,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
| Cash and cash equivalents | — | — | — | — | 
                                                24,290,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                38,010,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                40,515,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                40,987,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | 
                                                37,791,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
| Number of employees | 
                                                128
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                117
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                1,522
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                1,247
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                1,252
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                1,529
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | 
                                                1,544
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                1,280
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                1,558
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                1,298
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                1,581
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                1,298
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
| Average number of temporary employees | 
                                                21
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                11
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                495
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                194
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                202
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                515
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | 
                                                503
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                195
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                504
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                189
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                482
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                180
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
| Total shareholder return | — | — | — | — | — | 
                                                0.641
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                0.648
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | — | — | 
                                                0.703
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | 
                                                0.785
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | 
                                                0.748
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
| Total return on share price index | — | — | — | — | — | 
                                                1.962
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                1.388
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | — | — | 
                                                1.312
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | 
                                                1.286
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | 
                                                0.905
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             |