Key Financial Data Of Reporting Company
| Concept | As at 2025-03-31 | 2024-04-01 to 2025-03-31 | As at 2025-03-31 | As at 2025-03-31 | As at 2025-03-31 | As at 2024-03-31 | 2023-04-01 to 2024-03-31 | As at 2023-03-31 | 2022-04-01 to 2023-03-31 | 2021-04-01 to 2022-03-31 | As at 2022-03-31 | 2020-04-01 to 2021-03-31 | As at 2021-03-31 | 
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Key financial data of reporting company | |||||||||||||
| Business results of reporting company | |||||||||||||
| Net sales | — | 
                                                7,221,671,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | 
                                                7,071,728,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                6,584,391,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                6,467,394,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                8,417,567,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
| Ordinary profit (loss) | — | 
                                                610,845,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | 
                                                467,571,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                430,801,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                480,209,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                574,001,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
| Profit (loss) | — | 
                                                411,747,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | 
                                                337,608,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                311,581,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                309,867,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                410,099,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
| Equity in earnings (losses) of affiliates if equity method is applied | — | 
                                                
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | 
                                                
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
| Share capital | — | — | — | — | 
                                                1,204,900,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                1,204,900,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                1,204,900,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                1,204,900,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                1,204,900,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Total number of issued shares | — | — | — | — | 
                                                13,233,000
                                                
                                                    
                                                        xbrli:shares
                                                    
                                                
                                             | 
                                                13,233,000
                                                
                                                    
                                                        xbrli:shares
                                                    
                                                
                                             | — | 
                                                13,233,000
                                                
                                                    
                                                        xbrli:shares
                                                    
                                                
                                             | — | — | 
                                                13,233,000
                                                
                                                    
                                                        xbrli:shares
                                                    
                                                
                                             | — | 
                                                13,233,000
                                                
                                                    
                                                        xbrli:shares
                                                    
                                                
                                             | 
| Net assets | — | — | — | — | 
                                                12,126,382,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                10,853,149,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                10,365,732,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                10,175,112,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                10,180,584,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Total assets | — | — | — | — | 
                                                15,907,953,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                14,416,338,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                13,480,011,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                13,626,980,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                14,144,485,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Net assets per share | — | — | — | — | 
                                                921.61
                                                
                                             | 
                                                825.51
                                                
                                             | — | 
                                                788.43
                                                
                                             | — | — | 
                                                773.93
                                                
                                             | — | 
                                                744.34
                                                
                                             | 
| Dividend paid per share | — | 
                                                17.00
                                                
                                             | — | — | — | — | 
                                                18.00
                                                
                                             | — | 
                                                13.00
                                                
                                             | 
                                                13.00
                                                
                                             | — | 
                                                13.00
                                                
                                             | — | 
| Interim dividend paid per share | — |  | — | — | — | — |  | — |  |  | — |  | — | 
| Basic earnings (loss) per share | — | 
                                                31.30
                                                
                                             | — | — | — | — | 
                                                25.68
                                                
                                             | — | 
                                                23.70
                                                
                                             | 
                                                23.57
                                                
                                             | — | 
                                                31.19
                                                
                                             | — | 
| Diluted earnings per share | — |  | — | — | — | — |  | — |  |  | — |  | — | 
| Equity-to-asset ratio | — | — | — | — | 
                                                0.762
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.753
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                0.769
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                0.747
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                0.720
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
| Rate of return on equity | — | 
                                                0.036
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | — | 
                                                0.032
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                0.030
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.030
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                0.041
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
| Price-earnings ratio | — | 
                                                19.9
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | — | 
                                                28.5
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                29.1
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                29.7
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                27.1
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
| Payout ratio | — | 
                                                0.543
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | — | 
                                                0.701
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                0.549
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.552
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                0.417
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
| Net cash provided by (used in) operating activities | — | 
                                                883,429,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | 
                                                414,785,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                740,075,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                388,024,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                647,255,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
| Net cash provided by (used in) investing activities | — | 
                                                -406,369,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | 
                                                -42,315,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                -352,052,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                -322,101,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                136,798,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
| Net cash provided by (used in) financing activities | — | 
                                                -270,691,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | 
                                                -186,571,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                -191,824,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                -499,943,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                -196,107,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
| Cash and cash equivalents | — | — | — | — | 
                                                2,794,701,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                2,588,332,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                2,402,434,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                2,206,235,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                2,640,255,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Number of employees | 
                                                
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                6
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                183
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                189
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                194
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                199
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                209
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                211
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
| Average number of temporary employees | — | — | — | 
                                                22
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                22
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                23
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                23
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                25
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                20
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
| Total shareholder return | — | — | — | — | 
                                                1.084
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                1.225
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                1.132
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                1.127
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                1.332
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
| Total return on share price index | — | — | — | — | 
                                                2.134
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                2.168
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                1.534
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                1.450
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                1.421
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             |