Quarterly Consolidated Balance Sheet
| Concept | As at 2025-02-28 | As at 2025-02-28 | As at 2025-02-28 | As at 2025-02-28 | As at 2025-02-28 | As at 2025-02-28 | As at 2025-02-28 | As at 2025-02-28 | As at 2025-02-28 | As at 2025-02-28 | As at 2025-02-28 | As at 2025-02-28 | As at 2025-02-28 | As at 2025-02-28 | As at 2025-02-28 | As at 2025-02-28 | As at 2025-02-28 | As at 2024-02-29 | As at 2024-02-29 | As at 2024-02-29 | As at 2024-02-29 | As at 2024-02-29 | As at 2024-02-29 | As at 2024-02-29 | As at 2024-02-29 | As at 2024-02-29 | As at 2024-02-29 | As at 2024-02-29 | As at 2024-02-29 | As at 2024-02-29 | As at 2024-02-29 | As at 2024-02-29 | As at 2024-02-29 | As at 2024-02-29 | As at 2023-02-28 | As at 2023-02-28 | As at 2023-02-28 | As at 2023-02-28 | As at 2023-02-28 | As at 2023-02-28 | As at 2023-02-28 | As at 2023-02-28 | As at 2023-02-28 | As at 2023-02-28 | As at 2023-02-28 | As at 2023-02-28 | As at 2023-02-28 | As at 2023-02-28 | As at 2023-02-28 | As at 2023-02-28 | As at 2023-02-28 | 
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Quarterly consolidated balance sheet | |||||||||||||||||||||||||||||||||||||||||||||||||||
| Balance sheet | |||||||||||||||||||||||||||||||||||||||||||||||||||
| Assets | |||||||||||||||||||||||||||||||||||||||||||||||||||
| Current assets | |||||||||||||||||||||||||||||||||||||||||||||||||||
| Cash and deposits | — | — | — | — | — | — | — | — | — | — | — | — | — | 
                                                3,079,626,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                5,277,369,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | 
                                                4,518,538,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | 
                                                2,836,515,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | 
| Raw materials and supplies | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | 
                                                132,429,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | 
                                                116,601,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | 
| Other | — | — | — | — | — | — | — | — | — | — | — | — | — | 
                                                76,447,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                372,914,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | 
                                                360,956,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | 
                                                121,248,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | 
| Current assets | — | — | — | — | — | — | — | — | — | — | — | — | — | 
                                                5,776,489,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                6,760,924,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | 
                                                5,906,724,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | 
                                                5,274,451,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | 
| Non-current assets | |||||||||||||||||||||||||||||||||||||||||||||||||||
| Property, plant and equipment | — | — | — | — | — | — | — | — | — | — | — | — | — | 
                                                3,025,438,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                3,284,545,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | 
                                                3,521,952,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | 
                                                3,274,782,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | 
| Property, plant and equipment | |||||||||||||||||||||||||||||||||||||||||||||||||||
| Buildings and structures | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | 
                                                7,770,924,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | 
                                                7,661,947,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | 
| Accumulated depreciation | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | 
                                                -4,799,514,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | 
                                                -4,535,119,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | 
| Buildings and structures, net | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | 
                                                2,971,410,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | 
                                                3,126,828,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | 
| Land | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | 
                                                11,570,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | 
                                                11,570,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | 
| Leased assets | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | 
                                                200,086,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | 
                                                204,166,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | 
| Accumulated depreciation | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | 
                                                -189,718,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | 
                                                -190,818,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | 
| Leased assets, net | — | — | — | — | — | — | — | — | — | — | — | — | — | 
                                                10,367,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                10,367,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | 
                                                13,348,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | 
                                                13,348,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | 
| Construction in progress | — | — | — | — | — | — | — | — | — | — | — | — | — | 
                                                
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                324,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | 
                                                2,986,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | 
                                                2,986,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | 
| Other | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | 
                                                10,755,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | 
                                                12,284,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | 
| Accumulated depreciation | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | 
                                                -10,755,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | 
                                                -11,180,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | 
| Other, net | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | 
                                                0
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | 
                                                1,103,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | 
| Intangible assets | |||||||||||||||||||||||||||||||||||||||||||||||||||
| Goodwill | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | 
                                                250,764,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | 
                                                270,838,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | 
| Other | — | — | — | — | — | — | — | — | — | — | — | — | — | 
                                                16,928,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                17,712,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | 
                                                10,079,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | 
                                                8,483,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | 
| Intangible assets | — | — | — | — | — | — | — | — | — | — | — | — | — | 
                                                17,712,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                268,477,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | 
                                                280,917,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | 
                                                9,449,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | 
| Investments and other assets | — | — | — | — | — | — | — | — | — | — | — | — | — | 
                                                4,009,369,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                3,649,767,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | 
                                                3,593,883,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | 
                                                3,914,667,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | 
| Investments and other assets | |||||||||||||||||||||||||||||||||||||||||||||||||||
| Deferred tax assets | — | — | — | — | — | — | — | — | — | — | — | — | — | 
                                                543,701,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                585,118,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | 
                                                662,807,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | 
                                                554,747,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | 
| Other | — | — | — | — | — | — | — | — | — | — | — | — | — | 
                                                96,529,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                145,795,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | 
                                                129,533,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | 
                                                80,395,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | 
| Non-current assets | — | — | — | — | — | — | — | — | — | — | — | — | — | 
                                                7,052,519,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                7,202,790,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | 
                                                7,396,753,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | 
                                                7,198,899,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | 
| Assets | — | — | — | — | — | — | — | — | — | — | — | — | — | 
                                                12,829,008,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                13,963,714,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | 
                                                13,303,477,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | 
                                                12,473,351,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | 
| Liabilities | |||||||||||||||||||||||||||||||||||||||||||||||||||
| Current liabilities | |||||||||||||||||||||||||||||||||||||||||||||||||||
| Short-term borrowings | — | — | — | — | — | — | — | — | — | — | — | — | — | 
                                                700,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                700,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | 
                                                905,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | 
                                                700,000,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | 
| Income taxes payable | — | — | — | — | — | — | — | — | — | — | — | — | — | 
                                                273,835,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                420,671,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | 
                                                462,684,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | 
                                                376,595,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | 
| Asset retirement obligations | — | — | — | — | — | — | — | — | — | — | — | — | — | 
                                                6,386,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                14,036,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | 
                                                18,903,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | 
                                                18,903,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | 
| Other | — | — | — | — | — | — | — | — | — | — | — | — | — | 
                                                176,199,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                921,852,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | 
                                                825,467,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | 
                                                47,956,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | 
| Current liabilities | — | — | — | — | — | — | — | — | — | — | — | — | — | 
                                                4,235,185,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                4,098,988,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | 
                                                4,407,913,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | 
                                                4,308,422,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | 
| Non-current liabilities | |||||||||||||||||||||||||||||||||||||||||||||||||||
| Long-term borrowings | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | 
                                                34,654,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | 
                                                22,540,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | 
| Retirement benefit liability | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | 
                                                342,029,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | 
                                                364,318,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | 
| Asset retirement obligations | — | — | — | — | — | — | — | — | — | — | — | — | — | 
                                                593,193,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                677,311,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | 
                                                682,971,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | 
                                                590,876,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | 
| Other | — | — | — | — | — | — | — | — | — | — | — | — | — | 
                                                73,342,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                78,079,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | 
                                                78,614,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | 
                                                73,877,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | 
| Non-current liabilities | — | — | — | — | — | — | — | — | — | — | — | — | — | 
                                                1,052,890,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                1,132,074,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | 
                                                1,151,172,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | 
                                                999,097,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | 
| Liabilities | — | — | — | — | — | — | — | — | — | — | — | — | — | 
                                                5,288,076,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                5,231,062,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | 
                                                5,559,085,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | 
                                                5,307,519,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | 
| Net assets | |||||||||||||||||||||||||||||||||||||||||||||||||||
| Shareholders' equity | |||||||||||||||||||||||||||||||||||||||||||||||||||
| Share capital | — | — | — | — | — | — | — | — | — | — | — | — | — | 
                                                49,340,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                49,340,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | 
                                                49,340,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | 
                                                49,340,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | 
| Capital surplus | — | — | — | — | — | — | — | — | — | — | — | — | — | 
                                                506,530,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                505,639,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | 
                                                505,659,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | 
                                                505,659,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | 
| Retained earnings | — | — | — | — | — | — | — | — | — | — | — | — | — | 
                                                7,011,282,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                8,174,640,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | 
                                                7,259,351,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | 
                                                6,661,010,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | 
| Treasury shares | — | — | — | — | — | — | — | — | — | — | — | — | — | 
                                                -26,219,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                -26,219,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | 
                                                -50,177,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | 
                                                -50,177,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | 
| Shareholders' equity | — | — | — | — | — | — | — | — | — | — | — | — | — | 
                                                7,540,932,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                8,703,400,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | 
                                                7,764,173,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | 
                                                7,165,831,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | 
| Valuation and translation adjustments | |||||||||||||||||||||||||||||||||||||||||||||||||||
| Remeasurements of defined benefit plans | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | 
                                                29,250,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | 
                                                -19,781,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | 
| Valuation and translation adjustments | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | 
                                                29,250,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | 
                                                -19,781,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | 
| Net assets | 
                                                493,190,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                29,250,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                -26,219,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                7,011,282,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                7,540,932,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                506,530,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                7,011,282,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                13,340,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                8,703,400,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                29,250,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                -26,219,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                49,340,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                505,639,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                7,540,932,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                8,174,640,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                49,340,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                8,732,651,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                -19,781,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                7,764,173,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                -19,781,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                49,340,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                505,659,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                492,319,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                6,661,010,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                7,165,831,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                13,340,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                49,340,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                -50,177,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                7,744,392,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                505,659,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                -50,177,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                6,661,010,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                7,259,351,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                7,165,831,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                12,540,181,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                6,289,515,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                25,707,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                6,382,819,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                6,289,515,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                12,514,473,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                -519,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                25,707,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                49,340,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                6,396,159,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                6,069,493,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                12,734,495,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                13,340,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                6,396,159,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                12,734,495,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                -519,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
                                                49,340,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | 
| Liabilities and net assets | — | — | — | — | — | — | — | — | — | — | — | — | — | 
                                                12,829,008,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | 
                                                13,963,714,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | 
                                                13,303,477,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | 
                                                12,473,351,000
                                                
                                                    
                                                        JPY
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — |