Key Financial Data Of Reporting Company
| Concept | 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 | 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 | — | — | — | 
                                                89,809,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                91,676,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                77,458,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                80,171,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                67,297,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                68,820,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                68,968,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                70,435,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                101,429,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                103,964,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
| Ordinary profit (loss) | — | — | — | 
                                                4,707,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                4,896,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                3,059,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                3,127,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                2,433,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                2,596,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                2,477,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                2,486,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                3,764,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                3,887,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
| Profit (loss) | — | — | — | 
                                                3,594,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | 
                                                2,527,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                1,760,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | 
                                                1,826,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                2,236,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
| Share capital | — | — | — | — | — | — | — | 
                                                3,857,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                3,857,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | 
                                                3,857,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                3,857,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                3,857,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Total number of issued shares | — | — | — | — | — | — | — | 
                                                13,600,000
                                                
                                                    
                                                        xbrli:shares
                                                    
                                                
                                             | — | 
                                                13,600,000
                                                
                                                    
                                                        xbrli:shares
                                                    
                                                
                                             | — | — | — | — | — | 
                                                6,800,000
                                                
                                                    
                                                        xbrli:shares
                                                    
                                                
                                             | — | — | — | 
                                                6,800,000
                                                
                                                    
                                                        xbrli:shares
                                                    
                                                
                                             | — | — | — | 
                                                6,800,000
                                                
                                                    
                                                        xbrli:shares
                                                    
                                                
                                             | 
| Net assets | — | — | — | — | — | 
                                                38,756,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                38,068,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                35,035,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                35,380,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                34,360,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                33,860,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                33,666,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                33,299,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                30,684,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                30,406,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Total assets | — | — | — | — | — | 
                                                84,012,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                82,209,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                77,063,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                78,941,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                72,081,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                70,650,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                71,500,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                70,305,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                80,732,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                79,272,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Net assets per share | — | — | — | — | — | 
                                                1,506.49
                                                
                                             | — | 
                                                1,479.74
                                                
                                             | — | 
                                                1,363.27
                                                
                                             | 
                                                1,376.70
                                                
                                             | — | — | — | 
                                                1,339.15
                                                
                                             | 
                                                1,319.65
                                                
                                             | 
                                                1,314.95
                                                
                                             | — | — | 
                                                1,300.63
                                                
                                             | — | 
                                                1,201.30
                                                
                                             | — | 
                                                1,190.41
                                                
                                             | 
| Dividend paid per share | — | — | — | 
                                                120
                                                
                                             | — | — | — | — | 
                                                80
                                                
                                             | — | — | — | 
                                                120
                                                
                                             | — | — | — | — | 
                                                100
                                                
                                             | — | — | 
                                                125
                                                
                                             | — | — | — | 
| Interim dividend paid per share | — | — | — | 
                                                40.0
                                                
                                             | — | — | — | — | 
                                                25.0
                                                
                                             | — | — | — | 
                                                50.0
                                                
                                             | — | — | — | — | 
                                                50.0
                                                
                                             | — | — | 
                                                50.0
                                                
                                             | — | — | — | 
| Basic earnings (loss) per share | — | — | — | 
                                                139.77
                                                
                                             | 
                                                144.35
                                                
                                             | — | — | — | 
                                                98.40
                                                
                                             | — | — | 
                                                96.58
                                                
                                             | 
                                                68.64
                                                
                                             | 
                                                72.56
                                                
                                             | — | — | — | 
                                                71.38
                                                
                                             | 
                                                71.19
                                                
                                             | — | 
                                                87.54
                                                
                                             | — | 
                                                90.81
                                                
                                             | — | 
| Diluted earnings per share | — | — | — |  |  | — | — | — |  | — | — |  |  |  | — | — | — |  |  | — |  | — |  | — | 
| Equity-to-asset ratio | — | — | — | — | — | 
                                                0.461
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                0.463
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                0.455
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.448
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | 
                                                0.477
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.479
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.471
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                0.474
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                0.380
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                0.384
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
| Rate of return on equity | — | — | — | 
                                                0.098
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.100
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | 
                                                0.073
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                0.071
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.052
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.055
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | 
                                                0.057
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.057
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                0.074
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                0.076
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
| Price-earnings ratio | — | — | — | 
                                                12.0
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                11.6
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | 
                                                11.1
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                11.3
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                11.7
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                11.0
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | 
                                                10.7
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                10.7
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                9.1
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                8.8
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
| Payout ratio | — | — | — | 
                                                0.429
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | — | 
                                                0.407
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | 
                                                0.437
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | — | 
                                                0.350
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                0.357
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | 
| Net cash provided by (used in) operating activities | — | — | — | — | 
                                                2,010,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | 
                                                -34,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                4,648,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | 
                                                -1,459,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                8,112,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
| Net cash provided by (used in) investing activities | — | — | — | — | 
                                                -304,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | 
                                                -481,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                89,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | 
                                                -170,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                -385,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
| Net cash provided by (used in) financing activities | — | — | — | — | 
                                                -1,293,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | 
                                                -1,349,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                -1,297,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | 
                                                -1,453,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                -1,457,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
| Cash and cash equivalents | — | — | — | — | — | 
                                                17,979,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | 
                                                17,540,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                19,390,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                15,919,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | 
                                                18,997,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
| Number of employees | 
                                                861
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                74
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                913
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                987
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                74
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                935
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                946
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                993
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | 
                                                987
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                939
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                997
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                952
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                972
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                930
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
| Average number of temporary employees | 
                                                86
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                9
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                86
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                95
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                9
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                95
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                94
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                94
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | 
                                                96
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                95
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                101
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                100
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                107
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                106
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
| Total shareholder return | — | — | — | — | — | — | — | 
                                                2.499
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                1.636
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | — | — | 
                                                1.191
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | 
                                                1.100
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | 
                                                1.114
                                                
                                                    
                                                        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
                                                    
                                                
                                             |