Statement Of Cash Flows
| Concept | 2024-01-01 to 2024-12-31 | As at 2024-12-31 | 2023-01-01 to 2023-12-31 | As at 2023-12-31 | As at 2022-12-31 | 
|---|---|---|---|---|---|
| Statement of cash flows | |||||
| Statement of cash flows | |||||
| Cash flows from operating activities | |||||
| Subtotal | 
                                                389,332,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                246,078,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
| Interest and dividends received | 
                                                1,161,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                417,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
| Interest paid | 
                                                -18,263,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                -16,501,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
| Income taxes paid | 
                                                -46,787,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                -7,390,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
| Net cash provided by (used in) operating activities | 
                                                329,001,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                249,993,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
| Cash flows from operating activities | |||||
| Cash flows from operating activities | |||||
| Cash flows from facilities maintenance and investing activities | |||||
| Purchase of property, plant and equipment | 
                                                -4,139,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                -466,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
| Purchase of investment securities | 
                                                -72,494,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
| Proceeds from sale of investment securities | 
                                                28,800,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                12,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
| Other, net | 
                                                -14,850,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                -8,212,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
| Cash flows from investing activities | |||||
| Net cash provided by (used in) investing activities | 
                                                -190,061,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                -247,970,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
| Cash flows from financing activities | |||||
| Proceeds from issuance of bonds | 
                                                500,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
| Proceeds from long-term borrowings | 
                                                1,500,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
| Repayments of long-term borrowings | 
                                                -755,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                -160,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
| Redemption of bonds | 
                                                -290,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                -490,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
| Net cash provided by (used in) financing activities | 
                                                719,999,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                -414,999,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
| Net increase (decrease) in cash and cash equivalents | 
                                                858,940,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                -412,976,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
| Cash and cash equivalents | — | 
                                                2,389,452,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                1,530,512,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                1,943,488,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             |