Key Financial Data Of Reporting Company
| Concept | 2024-04-01 to 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 | 
                                                5,969,419,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                5,660,130,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                5,475,278,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                5,188,579,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                5,006,217,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
| Ordinary profit (loss) | 
                                                564,414,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                550,939,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                592,281,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                587,935,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                532,967,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
| Profit (loss) | 
                                                413,669,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                388,586,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                401,538,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                403,595,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                364,257,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
| Equity in earnings (losses) of affiliates if equity method is applied | 
                                                
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
| Share capital | — | 
                                                377,525,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                377,525,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                377,525,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                377,525,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                377,525,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Total number of issued shares | — | 
                                                3,975,300
                                                
                                                    
                                                        xbrli:shares
                                                    
                                                
                                             | 
                                                3,975,300
                                                
                                                    
                                                        xbrli:shares
                                                    
                                                
                                             | — | 
                                                3,975,300
                                                
                                                    
                                                        xbrli:shares
                                                    
                                                
                                             | — | — | 
                                                3,975,300
                                                
                                                    
                                                        xbrli:shares
                                                    
                                                
                                             | — | 
                                                3,975,300
                                                
                                                    
                                                        xbrli:shares
                                                    
                                                
                                             | 
| Net assets | — | 
                                                3,979,882,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                3,810,570,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                3,634,991,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                3,352,709,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                3,068,369,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Total assets | — | 
                                                5,904,654,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                6,144,020,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                5,768,040,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                5,585,679,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                5,121,177,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Net assets per share | — | 
                                                1,024.37
                                                
                                             | 
                                                969.56
                                                
                                             | — | 
                                                914.42
                                                
                                             | — | — | 
                                                843.41
                                                
                                             | — | 
                                                771.88
                                                
                                             | 
| Dividend paid per share | 
                                                54
                                                
                                             | — | — | 
                                                50
                                                
                                             | — | 
                                                40
                                                
                                             | 
                                                30
                                                
                                             | — | 
                                                30
                                                
                                             | — | 
| Interim dividend paid per share |  | — | — |  | — |  |  | — |  | — | 
| Basic earnings (loss) per share | 
                                                105.73
                                                
                                             | — | — | 
                                                97.91
                                                
                                             | — | 
                                                101.01
                                                
                                             | 
                                                101.53
                                                
                                             | — | 
                                                91.63
                                                
                                             | — | 
| Diluted earnings per share |  | — | — |  | — |  |  | — |  | — | 
| Equity-to-asset ratio | — | 
                                                0.674
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.620
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                0.630
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                0.600
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                0.599
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
| Rate of return on equity | 
                                                0.106
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                0.104
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                0.115
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.126
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                0.124
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
| Price-earnings ratio | 
                                                10.19
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                12.56
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                8.83
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                6.97
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                8.94
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
| Payout ratio | 
                                                0.511
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                0.511
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                0.396
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.295
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                0.327
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
| Net cash provided by (used in) operating activities | 
                                                217,540,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                549,417,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                344,756,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                560,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                367,383,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
| Net cash provided by (used in) investing activities | 
                                                -95,169,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                1,706,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                -4,463,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                -7,746,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                -47,763,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
| Net cash provided by (used in) financing activities | 
                                                -444,899,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                -214,645,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                -170,082,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                -120,272,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                -96,636,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
| Cash and cash equivalents | — | 
                                                3,432,998,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                3,755,526,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                3,419,047,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                3,248,835,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                2,816,854,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Number of employees | — | 
                                                844
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                819
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                804
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                798
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                825
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
| Total shareholder return | — | 
                                                2.502
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                2.695
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                1.938
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                1.500
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                1.658
                                                
                                                    
                                                        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
                                                    
                                                
                                             |