Quarterly Consolidated Balance Sheet
| Concept | As at 2025-03-31 | As at 2025-03-31 | As at 2025-03-31 | As at 2025-03-31 | As at 2025-03-31 | As at 2025-03-31 | As at 2025-03-31 | As at 2025-03-31 | As at 2025-03-31 | As at 2025-03-31 | As at 2025-03-31 | As at 2025-03-31 | As at 2025-03-31 | As at 2025-03-31 | As at 2025-03-31 | As at 2025-03-31 | As at 2025-03-31 | As at 2025-03-31 | As at 2025-03-31 | As at 2025-03-31 | As at 2025-03-31 | As at 2025-03-31 | As at 2025-03-31 | As at 2025-03-31 | As at 2025-03-31 | As at 2024-03-31 | As at 2024-03-31 | As at 2024-03-31 | As at 2024-03-31 | As at 2024-03-31 | As at 2024-03-31 | As at 2024-03-31 | As at 2024-03-31 | As at 2024-03-31 | As at 2024-03-31 | As at 2024-03-31 | As at 2024-03-31 | As at 2024-03-31 | As at 2024-03-31 | As at 2024-03-31 | As at 2024-03-31 | As at 2024-03-31 | As at 2024-03-31 | As at 2024-03-31 | As at 2024-03-31 | As at 2024-03-31 | As at 2024-03-31 | As at 2024-03-31 | As at 2024-03-31 | As at 2024-03-31 | As at 2023-03-31 | As at 2023-03-31 | As at 2023-03-31 | As at 2023-03-31 | As at 2023-03-31 | As at 2023-03-31 | As at 2023-03-31 | As at 2023-03-31 | As at 2023-03-31 | As at 2023-03-31 | As at 2023-03-31 | As at 2023-03-31 | As at 2023-03-31 | As at 2023-03-31 | As at 2023-03-31 | As at 2023-03-31 | As at 2023-03-31 | As at 2023-03-31 | As at 2023-03-31 | As at 2023-03-31 | As at 2023-03-31 | As at 2023-03-31 | 
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Quarterly consolidated balance sheet | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Balance sheet | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Assets | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Current assets | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Cash and deposits | — | — | — | — | — | — | — | — | — | — | — | — | 
                                                6,346,666,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | 
                                                5,392,409,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | 
                                                6,556,974,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | 
                                                5,741,343,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | 
| Raw materials and supplies | — | — | — | — | — | — | — | — | — | — | — | — | 
                                                61,687,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | 
                                                52,716,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | 
                                                42,817,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | 
                                                38,684,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | 
| Other | — | — | — | — | — | — | — | — | — | — | — | — | 
                                                590,271,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | 
                                                2,743,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | 
                                                860,409,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | 
                                                258,370,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | 
| Allowance for doubtful accounts | — | — | — | — | — | — | — | — | — | — | — | — | 
                                                -2,723,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | 
                                                -2,666,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | 
                                                -2,684,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | 
                                                -2,616,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | 
| Current assets | — | — | — | — | — | — | — | — | — | — | — | — | 
                                                12,708,907,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | 
                                                10,908,003,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | 
                                                13,071,750,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | 
                                                11,356,416,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | 
| Non-current assets | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Property, plant and equipment | — | — | — | — | — | — | — | — | — | — | — | — | 
                                                24,732,245,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | 
                                                23,627,304,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | 
                                                23,897,591,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | 
                                                22,794,476,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | 
| Property, plant and equipment | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Buildings and structures | — | — | — | — | — | — | — | — | — | — | — | — | 
                                                30,896,891,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | 
                                                30,890,514,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | 
| Accumulated depreciation | — | — | — | — | — | — | — | — | — | — | — | — | 
                                                -20,665,312,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | 
                                                -20,042,349,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | 
| Buildings and structures, net | — | — | — | — | — | — | — | — | — | — | — | — | 
                                                10,231,579,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | 
                                                10,848,165,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | 
| Machinery, equipment and vehicles | — | — | — | — | — | — | — | — | — | — | — | — | 
                                                6,218,863,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | 
                                                6,062,627,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | 
| Accumulated depreciation | — | — | — | — | — | — | — | — | — | — | — | — | 
                                                -5,248,952,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | 
                                                -5,066,326,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | 
| Accumulated impairment | — | — | — | — | — | — | — | — | — | — | — | — | 
                                                -6,807,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | 
                                                -6,807,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | 
| Machinery, equipment and vehicles, net | — | — | — | — | — | — | — | — | — | — | — | — | 
                                                963,103,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | 
                                                989,492,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | 
| Land | — | — | — | — | — | — | — | — | — | — | — | — | 
                                                10,130,914,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | 
                                                9,885,897,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | 
                                                10,134,624,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | 
                                                9,889,607,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | 
| Leased assets | — | — | — | — | — | — | — | — | — | — | — | — | 
                                                56,431,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | 
                                                56,431,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | 
| Accumulated depreciation | — | — | — | — | — | — | — | — | — | — | — | — | 
                                                -51,728,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | 
                                                -43,667,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | 
| Leased assets, net | — | — | — | — | — | — | — | — | — | — | — | — | 
                                                4,702,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | 
                                                4,702,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | 
                                                12,764,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | 
                                                12,764,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | 
| Construction in progress | — | — | — | — | — | — | — | — | — | — | — | — | 
                                                2,911,413,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | 
                                                2,911,413,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | 
                                                1,405,394,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | 
                                                1,405,394,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | 
| Intangible assets | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Intangible assets | — | — | — | — | — | — | — | — | — | — | — | — | 
                                                252,557,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | 
                                                234,147,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | 
                                                282,042,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | 
                                                261,641,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | 
| Investments and other assets | — | — | — | — | — | — | — | — | — | — | — | — | 
                                                10,893,417,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | 
                                                8,540,049,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | 
                                                10,283,561,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | 
                                                8,168,104,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | 
| Investments and other assets | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Investment securities | — | — | — | — | — | — | — | — | — | — | — | — | 
                                                8,708,425,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | 
                                                5,925,998,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | 
                                                8,058,201,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | 
                                                5,500,427,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | 
| Long-term loans receivable | — | — | — | — | — | — | — | — | — | — | — | — | 
                                                
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | 
                                                
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | 
                                                3,360,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | 
                                                2,400,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | 
| Deferred tax assets | — | — | — | — | — | — | — | — | — | — | — | — | 
                                                457,489,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | 
                                                426,081,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | 
| Other | — | — | — | — | — | — | — | — | — | — | — | — | 
                                                227,808,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | 
                                                74,159,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | 
                                                268,032,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | 
                                                83,241,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | 
| Allowance for doubtful accounts | — | — | — | — | — | — | — | — | — | — | — | — | 
                                                -1,701,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | 
                                                -1,695,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | 
                                                -2,631,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | 
                                                -2,624,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | 
| Non-current assets | — | — | — | — | — | — | — | — | — | — | — | — | 
                                                35,878,221,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | 
                                                32,401,501,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | 
                                                34,463,195,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | 
                                                31,224,222,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | 
| Assets | — | 
                                                1,985,755,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                29,681,828,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | 
                                                48,587,129,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | 
                                                31,667,583,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                43,309,504,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | — | — | 
                                                28,312,420,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | 
                                                47,534,946,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                30,400,258,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                42,580,638,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                2,087,837,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | 
| Liabilities | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Current liabilities | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Short-term borrowings | — | — | — | — | — | — | — | — | — | — | — | — | 
                                                4,466,600,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | 
                                                300,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | 
                                                4,393,900,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | 
                                                600,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | 
| Income taxes payable | — | — | — | — | — | — | — | — | — | — | — | — | 
                                                420,919,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | 
                                                266,749,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | 
                                                113,077,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | 
                                                111,291,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | 
| Other | — | — | — | — | — | — | — | — | — | — | — | — | 
                                                1,407,874,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | 
                                                293,327,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | 
                                                1,137,241,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | 
                                                30,155,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | 
| Current liabilities | — | — | — | — | — | — | — | — | — | — | — | — | 
                                                8,472,272,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | 
                                                8,264,296,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | 
                                                7,781,959,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | 
                                                7,527,707,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | 
| Non-current liabilities | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Long-term borrowings | — | — | — | — | — | — | — | — | — | — | — | — | 
                                                10,264,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | 
                                                10,264,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | 
                                                11,230,600,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | 
                                                11,230,600,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | 
| Retirement benefit liability | — | — | — | — | — | — | — | — | — | — | — | — | 
                                                927,165,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | 
                                                1,168,867,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | 
| Asset retirement obligations | — | — | — | — | — | — | — | — | — | — | — | — | 
                                                127,845,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | 
                                                32,357,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | 
                                                125,639,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | 
                                                31,965,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | 
| Other | — | — | — | — | — | — | — | — | — | — | — | — | 
                                                668,051,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | 
                                                16,517,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | 
                                                615,081,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | 
                                                34,681,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | 
| Non-current liabilities | — | — | — | — | — | — | — | — | — | — | — | — | 
                                                13,469,013,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | 
                                                12,906,815,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | 
                                                14,555,554,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | 
                                                13,891,741,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | 
| Liabilities | — | — | — | — | — | — | — | — | — | — | — | — | 
                                                21,941,286,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | 
                                                21,171,112,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | 
                                                22,337,514,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | 
                                                21,419,449,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | 
| Net assets | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Shareholders' equity | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Share capital | — | — | — | — | — | — | — | — | — | — | — | — | 
                                                3,412,524,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | 
                                                3,412,524,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | 
                                                3,412,524,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | 
                                                3,412,524,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | 
| Capital surplus | — | — | — | — | — | — | — | — | — | — | — | — | 
                                                2,217,339,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | 
                                                2,217,339,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | 
                                                2,214,253,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | 
                                                2,214,253,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | 
| Retained earnings | — | — | — | — | — | — | — | — | — | — | — | — | 
                                                18,985,562,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | 
                                                14,843,381,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | 
                                                17,926,994,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | 
                                                14,162,200,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | 
| Treasury shares | — | — | — | — | — | — | — | — | — | — | — | — | 
                                                -384,724,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | 
                                                -331,841,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | 
                                                -404,885,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | 
                                                -352,002,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | 
| Shareholders' equity | — | — | — | — | — | — | — | — | — | — | — | — | 
                                                24,230,702,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | 
                                                20,141,404,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | 
                                                23,148,887,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | 
                                                19,436,975,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | 
| Valuation and translation adjustments | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Valuation difference on available-for-sale securities | — | — | — | — | — | — | — | — | — | — | — | — | 
                                                2,027,943,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | 
                                                1,996,987,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | 
                                                1,761,675,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | 
                                                1,724,213,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | 
| Remeasurements of defined benefit plans | — | — | — | — | — | — | — | — | — | — | — | — | 
                                                387,196,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | 
                                                286,868,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | 
| Valuation and translation adjustments | — | — | — | — | — | — | — | — | — | — | — | — | 
                                                2,415,139,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | 
                                                1,996,987,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | 
                                                2,048,544,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | 
                                                1,724,213,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | 
| Net assets | 
                                                2,027,943,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                387,196,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                1,367,870,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                20,141,404,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                82,782,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                14,843,381,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                2,453,500,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                518,855,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                18,985,562,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                10,503,155,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                26,645,842,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                3,412,524,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                24,230,702,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                2,415,139,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                -384,724,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                -331,841,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                22,138,392,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                2,217,339,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                3,412,524,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                1,996,987,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                2,134,557,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                2,217,339,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                286,868,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                19,436,975,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                2,134,557,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                2,214,253,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                17,926,994,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                2,453,500,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                14,162,200,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                -352,002,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                1,724,213,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                -404,885,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                1,761,675,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                1,431,737,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                79,695,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                2,214,253,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                3,412,524,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                25,197,432,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                23,148,887,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                2,048,544,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                518,855,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                21,161,189,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | 
                                                3,412,524,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                9,758,106,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                3,412,524,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                3,412,524,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                2,453,500,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                8,924,645,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                77,095,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                22,158,495,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                63,500,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                19,648,604,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                1,017,017,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                2,211,653,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                2,211,653,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                1,496,103,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                -421,025,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                2,134,557,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                23,239,013,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                -368,142,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                18,649,139,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                1,080,518,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                999,464,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                16,955,342,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                13,393,103,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                518,855,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Liabilities and net assets | — | — | — | — | — | — | — | — | — | — | — | — | 
                                                48,587,129,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | 
                                                43,309,504,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | 
                                                47,534,946,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | 
                                                42,580,638,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — |