| 関連事業営業利益又は関連事業営業損失(△) | ja | http://www.xbrl.org/2003/role/label | http://www.xbrl.org/2003/role/link |
| 関連事業営業利益又は関連事業営業損失(△)、高速道路事業 | ja | http://www.xbrl.org/2003/role/verboseLabel | http://www.xbrl.org/2003/role/link |
| 関連事業営業利益 | ja | http://www.xbrl.org/2003/role/positiveLabel | http://www.xbrl.org/2003/role/link |
| 関連事業営業損失(△) | ja | http://www.xbrl.org/2003/role/negativeLabel | http://www.xbrl.org/2003/role/link |
| Operating profit (loss) from related operations | en | http://www.xbrl.org/2003/role/label | http://www.xbrl.org/2003/role/link |
| Operating profit (loss) from related operations - HWY | en | http://www.xbrl.org/2003/role/verboseLabel | http://www.xbrl.org/2003/role/link |
| Operating profit from related operations | en | http://www.xbrl.org/2003/role/positiveLabel | http://www.xbrl.org/2003/role/link |
| Operating loss from related operations | en | http://www.xbrl.org/2003/role/negativeLabel | http://www.xbrl.org/2003/role/link |