| 退職給付信託設定損益(△は益) | ja | http://www.xbrl.org/2003/role/label | http://www.xbrl.org/2003/role/link |
| 退職給付信託設定損益(△は益)、営業活動によるキャッシュ・フロー | ja | http://www.xbrl.org/2003/role/verboseLabel | http://www.xbrl.org/2003/role/link |
| Loss (gain) on securities contribution to employees' retirement benefits trust | en | http://www.xbrl.org/2003/role/label | http://www.xbrl.org/2003/role/link |
| Loss (gain) on securities contribution to employees' retirement benefits trust-OpeCF | en | http://www.xbrl.org/2003/role/verboseLabel | http://www.xbrl.org/2003/role/link |