Key Financial Data Of Reporting Company
| Concept | As at 2024-03-31 | As at 2024-03-31 | As at 2024-03-31 | As at 2024-03-31 | As at 2024-03-31 | As at 2024-03-31 | 2023-04-01 to 2024-03-31 | 2023-04-01 to 2024-03-31 | As at 2024-03-31 | As at 2024-03-31 | As at 2024-03-31 | As at 2024-03-31 | 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 | — | — | — | — | — | — | 
                                                8,840,943,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                15,390,986,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | 
                                                8,529,265,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                14,293,621,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                8,145,066,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                14,171,946,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                7,658,456,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                12,984,414,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                8,522,482,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                13,878,875,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
| Ordinary profit (loss) | — | — | — | — | — | — | 
                                                567,820,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                603,415,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | 
                                                489,483,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                549,390,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                420,095,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                491,094,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                275,835,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                332,546,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                575,007,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                622,635,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
| Profit (loss) | — | — | — | — | — | — | 
                                                375,719,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | 
                                                287,489,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                269,241,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | 
                                                165,781,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                355,399,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
| Share capital | — | — | — | — | — | — | — | — | — | — | — | — | 
                                                750,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                750,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | 
                                                750,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                750,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                750,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Total number of issued shares | — | — | — | — | — | — | — | — | — | — | — | — | 
                                                6,470,660
                                                
                                                    
                                                        xbrli:shares
                                                    
                                                
                                             | — | — | 
                                                6,470,660
                                                
                                                    
                                                        xbrli:shares
                                                    
                                                
                                             | — | — | — | — | — | 
                                                6,470,660
                                                
                                                    
                                                        xbrli:shares
                                                    
                                                
                                             | — | — | — | 
                                                6,470,660
                                                
                                                    
                                                        xbrli:shares
                                                    
                                                
                                             | — | — | — | 
                                                6,470,660
                                                
                                                    
                                                        xbrli:shares
                                                    
                                                
                                             | 
| Net assets | — | — | — | — | — | — | — | — | 
                                                7,859,808,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                7,561,199,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                7,203,066,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                7,508,556,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                7,268,631,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                6,980,883,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                7,075,810,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                6,815,775,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                6,946,003,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                6,705,894,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Total assets | — | — | — | — | — | — | — | — | 
                                                14,942,314,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                13,640,211,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                13,413,388,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                14,426,489,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                14,517,385,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                13,548,193,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                13,825,704,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                12,823,900,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                10,614,718,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                9,929,678,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Net assets per share | — | — | — | — | — | — | — | — | 
                                                1,401.54
                                                
                                             | — | — | — | 
                                                1,348.29
                                                
                                             | — | — | 
                                                1,284.43
                                                
                                             | 
                                                1,338.90
                                                
                                             | — | — | — | 
                                                1,296.12
                                                
                                             | 
                                                1,244.81
                                                
                                             | 
                                                1,296.41
                                                
                                             | — | — | 
                                                1,248.77
                                                
                                             | — | 
                                                1,272.63
                                                
                                             | — | 
                                                1,228.64
                                                
                                             | 
| Dividend paid per share | — | — | — | — | — | — | 
                                                15.00
                                                
                                             | — | — | — | — | — | — | — | 
                                                12.50
                                                
                                             | — | — | — | 
                                                12.50
                                                
                                             | — | — | — | — | 
                                                12.50
                                                
                                             | — | — | 
                                                12.50
                                                
                                             | — | — | — | 
| Interim dividend paid per share | — | — | — | — | — | — |  | — | — | — | — | — | — | — |  | — | — | — |  | — | — | — | — |  | — | — |  | — | — | — | 
| Basic earnings (loss) per share | — | — | — | — | — | — | 
                                                67.00
                                                
                                             | 
                                                67.33
                                                
                                             | — | — | — | — | — | — | 
                                                51.26
                                                
                                             | — | — | 
                                                55.79
                                                
                                             | 
                                                48.33
                                                
                                             | 
                                                49.99
                                                
                                             | — | — | — | 
                                                30.37
                                                
                                             | 
                                                41.45
                                                
                                             | — | 
                                                62.50
                                                
                                             | — | 
                                                64.72
                                                
                                             | — | 
| Diluted earnings per share | — | — | — | — | — | — |  |  | — | — | — | — | — | — |  | — | — |  |  |  | — | — | — |  |  | — |  | — |  | — | 
| Equity-to-asset ratio | — | — | — | — | — | — | — | — | 
                                                0.526
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | 
                                                0.554
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                0.537
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.520
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | 
                                                0.501
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.515
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.512
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                0.531
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                0.654
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                0.675
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
| Rate of return on equity | — | — | — | — | — | — | 
                                                0.051
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.049
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | — | — | — | 
                                                0.041
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                0.042
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.039
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.039
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | 
                                                0.025
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.032
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                0.052
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                0.052
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
| Price-earnings ratio | — | — | — | — | — | — | 
                                                12.0
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                12.0
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | — | — | — | 
                                                11.1
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                10.2
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                12.3
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                11.9
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | 
                                                23.1
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                16.9
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                9.5
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                9.1
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
| Payout ratio | — | — | — | — | — | — | 
                                                0.224
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | — | — | — | — | 
                                                0.244
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | 
                                                0.259
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | — | 
                                                0.412
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                0.200
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | 
| Net cash provided by (used in) operating activities | — | — | — | — | — | — | — | 
                                                578,611,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | 
                                                580,086,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                862,716,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | 
                                                172,960,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                -284,080,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
| Net cash provided by (used in) investing activities | — | — | — | — | — | — | — | 
                                                -117,588,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | 
                                                89,906,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                -287,158,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | 
                                                -1,435,517,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                -516,876,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
| Net cash provided by (used in) financing activities | — | — | — | — | — | — | — | 
                                                -349,513,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | 
                                                -320,696,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                -176,801,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | 
                                                3,131,864,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                -499,999,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
| Cash and cash equivalents | — | — | — | — | — | — | — | — | 
                                                4,761,467,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | 
                                                4,599,022,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                4,266,724,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                3,867,967,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | 
                                                1,998,660,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
| Number of employees | 
                                                578
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                8
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                49
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                13
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                1
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                49
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                736
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                1
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                578
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                87
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                680
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                52
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                691
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                743
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | 
                                                741
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                696
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                745
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                707
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                736
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                720
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
| Average number of temporary employees | 
                                                10
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                19
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                10
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                9
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                19
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                9
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                19
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                19
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | 
                                                21
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                21
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                30
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                30
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                30
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                30
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
| Total shareholder return | — | — | — | — | — | — | — | — | — | — | — | — | 
                                                1.242
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                0.882
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | — | — | 
                                                0.898
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | 
                                                1.034
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | 
                                                0.860
                                                
                                                    
                                                        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
                                                    
                                                
                                             |