Key Financial Data Of Reporting Company
| Concept | 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 | As at 2020-03-31 | 2019-04-01 to 2020-03-31 | 
|---|---|---|---|---|---|---|---|---|---|---|
| Key financial data of reporting company | ||||||||||
| Business results of reporting company | ||||||||||
| Net sales | — | 
                                                5,660,130,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                5,475,278,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                5,188,579,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                5,006,217,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                5,437,767,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Ordinary profit (loss) | — | 
                                                550,939,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                592,281,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                587,935,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                532,967,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                558,219,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Profit (loss) | — | 
                                                388,586,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                401,538,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                403,595,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                364,257,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                379,700,000
                                                
                                                    
                                                        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 | 
                                                3,810,570,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                3,634,991,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                3,352,709,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                3,068,369,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                2,799,516,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
| Total assets | 
                                                6,144,020,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                5,768,040,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                5,585,679,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                5,121,177,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                4,913,398,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
| Net assets per share | 
                                                969.56
                                                
                                             | — | 
                                                914.42
                                                
                                             | — | — | 
                                                843.41
                                                
                                             | — | 
                                                771.88
                                                
                                             | 
                                                704.25
                                                
                                             | — | 
| Dividend paid per share | — | 
                                                50
                                                
                                             | — | 
                                                40
                                                
                                             | 
                                                30
                                                
                                             | — | 
                                                30
                                                
                                             | — | — | 
                                                24
                                                
                                             | 
| Interim dividend paid per share | — |  | — |  |  | — |  | — | — |  | 
| Basic earnings (loss) per share | — | 
                                                97.91
                                                
                                             | — | 
                                                101.01
                                                
                                             | 
                                                101.53
                                                
                                             | — | 
                                                91.63
                                                
                                             | — | — | 
                                                95.52
                                                
                                             | 
| Diluted earnings per share | — |  | — |  |  | — |  | — | — |  | 
| Equity-to-asset ratio | 
                                                0.620
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                0.630
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                0.600
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                0.599
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.570
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
| Rate of return on equity | — | 
                                                0.104
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                0.115
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.126
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                0.124
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                0.143
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
| Price-earnings ratio | — | 
                                                12.56
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                8.83
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                6.97
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                8.94
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                5.36
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
| Payout ratio | — | 
                                                0.511
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                0.396
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.295
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                0.327
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                0.251
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
| Net cash provided by (used in) operating activities | — | 
                                                549,417,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                344,756,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                560,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                367,383,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                367,616,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Net cash provided by (used in) investing activities | — | 
                                                1,706,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                -4,463,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                -7,746,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                -47,763,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                -3,683,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Net cash provided by (used in) financing activities | — | 
                                                -214,645,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                -170,082,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                -120,272,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                -96,636,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                -95,626,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Cash and cash equivalents | 
                                                3,755,526,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                3,419,047,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                3,248,835,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                2,816,854,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                2,593,870,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
| Number of employees | 
                                                819
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                804
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                798
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                825
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                812
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
| Total shareholder return | 
                                                1.440
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                1.042
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | 
                                                0.812
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                0.895
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.550
                                                
                                                    
                                                        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
                                                    
                                                
                                             | — |