Key Financial Data Of Reporting Company
| Concept | As at 2024-03-31 | As at 2024-03-31 | 2023-04-01 to 2024-03-31 | As at 2024-03-31 | As at 2024-03-31 | 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 | — | — | 
                                                10,689,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                11,090,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                10,445,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                10,797,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                10,121,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                10,542,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                9,421,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                9,968,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                8,699,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                9,172,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
| Ordinary profit (loss) | — | — | 
                                                2,815,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                2,785,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                2,855,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                2,722,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                2,511,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                2,535,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                2,412,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                2,127,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                1,681,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                1,818,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
| Profit (loss) | — | — | 
                                                1,968,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | 
                                                1,704,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                1,773,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | 
                                                1,788,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                1,163,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
| Share capital | — | — | — | — | — | — | — | — | 
                                                3,000,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                3,000,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | 
                                                425,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                425,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                425,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Total number of issued shares | — | — | — | — | — | — | — | — | 
                                                43,400,000
                                                
                                                    
                                                        xbrli:shares
                                                    
                                                
                                             | — | 
                                                43,400,000
                                                
                                                    
                                                        xbrli:shares
                                                    
                                                
                                             | — | — | — | — | — | 
                                                43,400,000
                                                
                                                    
                                                        xbrli:shares
                                                    
                                                
                                             | — | — | — | 
                                                43,400,000
                                                
                                                    
                                                        xbrli:shares
                                                    
                                                
                                             | — | — | — | 
                                                43,400,000
                                                
                                                    
                                                        xbrli:shares
                                                    
                                                
                                             | 
| Net assets | — | — | — | — | — | — | 
                                                12,230,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                12,294,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                10,535,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                10,582,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                9,743,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                9,752,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                8,789,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                8,755,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                7,842,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                7,476,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Total assets | — | — | — | — | — | — | 
                                                16,710,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                16,547,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                14,553,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                14,741,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                14,361,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                14,289,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                13,115,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                13,017,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                11,720,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                11,261,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Net assets per share | — | — | — | — | — | — | 
                                                288.61
                                                
                                             | — | 
                                                290.11
                                                
                                             | — | 
                                                248.61
                                                
                                             | 
                                                249.70
                                                
                                             | — | — | — | 
                                                229.92
                                                
                                             | 
                                                230.12
                                                
                                             | 
                                                205.94
                                                
                                             | — | — | 
                                                205.14
                                                
                                             | — | 
                                                183.75
                                                
                                             | — | 
                                                175.17
                                                
                                             | 
| Dividend paid per share | — | — | 
                                                22.50
                                                
                                             | — | — | — | — | — | — | 
                                                22.00
                                                
                                             | — | — | — | 
                                                18.00
                                                
                                             | — | — | — | — | 
                                                14.00
                                                
                                             | — | — | 
                                                12.20
                                                
                                             | — | — | — | 
| Interim dividend paid per share | — | — | 
                                                10.00
                                                
                                             | — | — | — | — | — | — | 
                                                10.50
                                                
                                             | — | — | — | 
                                                7.00
                                                
                                             | — | — | — | — | 
                                                6.00
                                                
                                             | — | — | 
                                                6.00
                                                
                                             | — | — | — | 
| Basic earnings (loss) per share | — | — | 
                                                46.46
                                                
                                             | — | — | 
                                                43.86
                                                
                                             | — | — | — | 
                                                40.21
                                                
                                             | — | — | 
                                                41.51
                                                
                                             | 
                                                41.80
                                                
                                             | 
                                                40.80
                                                
                                             | — | — | — | 
                                                41.92
                                                
                                             | 
                                                34.14
                                                
                                             | — | 
                                                27.26
                                                
                                             | — | 
                                                29.24
                                                
                                             | — | 
| Diluted earnings per share | — | — |  | — | — |  | — | — | — |  | — | — |  |  |  | — | — | — |  |  | — |  | — |  | — | 
| Equity-to-asset ratio | — | — | — | — | — | — | 
                                                0.732
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                0.743
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                0.724
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.718
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | 
                                                0.678
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.682
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.670
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                0.673
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                0.669
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                0.664
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
| Rate of return on equity | — | — | 
                                                0.172
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                0.163
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | 
                                                0.168
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                0.173
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.192
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.187
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | 
                                                0.220
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.175
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                0.163
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                0.167
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
| Price-earnings ratio | — | — | 
                                                17.2
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                18.2
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | 
                                                19.1
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                18.5
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                20.1
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                20.6
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | 
                                                20.4
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                25.0
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                20.1
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                18.7
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
| Payout ratio | — | — | 
                                                0.484
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | — | — | — | 
                                                0.547
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | 
                                                0.431
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | — | 
                                                0.334
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                0.448
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | 
| Net cash provided by (used in) operating activities | — | — | — | — | — | 
                                                2,982,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | 
                                                2,614,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                2,905,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | 
                                                2,328,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                1,973,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
| Net cash provided by (used in) investing activities | — | — | — | — | — | 
                                                -553,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | 
                                                222,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                -2,262,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | 
                                                -377,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                -420,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
| Net cash provided by (used in) financing activities | — | — | — | — | — | 
                                                -1,749,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | 
                                                -1,736,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                -1,686,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | 
                                                -1,271,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                -2,259,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
| Cash and cash equivalents | — | — | — | — | — | — | 
                                                6,952,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | 
                                                6,272,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                5,172,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                6,216,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | 
                                                5,536,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
| Number of employees | 
                                                23
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                23
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                9
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                221
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                272
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                240
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                244
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                254
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                286
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | 
                                                279
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                247
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                259
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                223
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                251
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                214
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
| Average number of temporary employees | 
                                                5
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                5
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                38
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                52
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                47
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                43
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                46
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                56
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | 
                                                57
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                46
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                42
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                41
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                42
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                31
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
| Total shareholder return | — | — | — | — | — | — | — | — | 
                                                1.466
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                1.385
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | — | — | 
                                                1.465
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | 
                                                1.457
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | 
                                                0.942
                                                
                                                    
                                                        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
                                                    
                                                
                                             |