| 無形固定資産 | ja | http://www.xbrl.org/2003/role/label | http://www.xbrl.org/2003/role/link |
| 無形固定資産、高速道路事業固定資産、高速道路事業 | ja | http://www.xbrl.org/2003/role/verboseLabel | http://www.xbrl.org/2003/role/link |
| 無形固定資産合計 | ja | http://www.xbrl.org/2003/role/totalLabel | http://www.xbrl.org/2003/role/link |
| Intangible assets | en | http://www.xbrl.org/2003/role/label | http://www.xbrl.org/2003/role/link |
| Intangible assets-highway business-NCA-HWY | en | http://www.xbrl.org/2003/role/verboseLabel | http://www.xbrl.org/2003/role/link |
| Total intangible assets | en | http://www.xbrl.org/2003/role/totalLabel | http://www.xbrl.org/2003/role/link |