Quarterly Consolidated Balance Sheet
| Concept | As at 2024-03-31 | As at 2023-12-31 | 
|---|---|---|
| Quarterly consolidated balance sheet | ||
| Balance sheet | ||
| Assets | ||
| Current assets | ||
| Cash and deposits | 
                                                3,506,969,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                3,511,816,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Other | 
                                                254,175,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                252,661,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Current assets | 
                                                4,290,107,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                4,286,922,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Non-current assets | ||
| Property, plant and equipment | 
                                                2,185,713,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                2,126,906,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Property, plant and equipment | ||
| Buildings and structures | — | — | 
| Buildings and structures, net | 
                                                1,748,137,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                1,714,089,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Other | — | — | 
| Other, net | 
                                                437,576,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                412,816,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Intangible assets | ||
| Intangible assets | 
                                                64,762,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                64,442,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Investments and other assets | 
                                                967,806,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                994,941,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Investments and other assets | ||
| Deferred tax assets | 
                                                267,879,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                301,130,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Other | 
                                                29,280,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                25,271,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Non-current assets | 
                                                3,218,283,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                3,186,289,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Assets | 
                                                7,508,391,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                7,473,212,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Liabilities | ||
| Current liabilities | ||
| Short-term borrowings | 
                                                50,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Income taxes payable | 
                                                72,854,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                197,615,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Other | 
                                                277,181,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                398,407,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Current liabilities | 
                                                2,086,108,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                2,038,963,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Non-current liabilities | ||
| Long-term borrowings | 
                                                544,098,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                615,577,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Asset retirement obligations | 
                                                372,184,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                371,033,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Other | 
                                                49,535,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                47,307,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Non-current liabilities | 
                                                965,818,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                1,033,918,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Liabilities | 
                                                3,051,927,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                3,072,881,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Net assets | ||
| Shareholders' equity | ||
| Share capital | 
                                                872,800,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                872,800,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Capital surplus | 
                                                1,027,313,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                1,027,313,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Retained earnings | 
                                                2,556,444,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                2,500,217,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Treasury shares | 
                                                -93,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Shareholders' equity | 
                                                4,456,464,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                4,400,330,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Net assets | 
                                                4,456,464,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                4,400,330,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Liabilities and net assets | 
                                                7,508,391,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                7,473,212,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             |