Quarterly Statement Of Cash Flows
| Concept | 2023-04-01 to 2023-09-30 | As at 2023-09-30 | As at 2023-03-31 | 2022-04-01 to 2022-09-30 | As at 2022-09-30 | As at 2022-03-31 | 
|---|---|---|---|---|---|---|
| Quarterly statement of cash flows | ||||||
| Statement of cash flows | ||||||
| Cash flows from operating activities | ||||||
| Subtotal | 
                                                73,211,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                618,396,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
| Interest and dividends received | 
                                                49,085,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                47,956,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
| Income taxes paid | 
                                                -71,447,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                -20,958,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
| Net cash provided by (used in) operating activities | 
                                                49,362,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                643,411,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
| Cash flows from investing activities | ||||||
| Purchase of property, plant and equipment | 
                                                -120,351,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                -120,569,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
| Proceeds from sale of investment securities | 
                                                157,261,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
| Other, net | 
                                                602,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                82,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
| Net cash provided by (used in) investing activities | 
                                                37,512,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                -120,487,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
| Cash flows from financing activities | ||||||
| Dividends paid | 
                                                -169,852,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                -169,625,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
| Net cash provided by (used in) financing activities | 
                                                -180,145,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                -180,693,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
| Net increase (decrease) in cash and cash equivalents | 
                                                -93,270,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                342,230,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
| Cash and cash equivalents | — | 
                                                2,309,163,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                2,402,434,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                2,548,466,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                2,206,235,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             |