| 社債、長期借入金及び短期借入金の増減明細表 | ja | http://www.xbrl.org/2003/role/label | http://www.xbrl.org/2003/role/link |
| 社債、長期借入金及び短期借入金の増減明細表、高速道路事業 [目次項目] | ja | http://www.xbrl.org/2003/role/verboseLabel | http://www.xbrl.org/2003/role/link |
| Annexed detailed schedule of corporate bonds and short-term and long-term borrowings | en | http://www.xbrl.org/2003/role/label | http://www.xbrl.org/2003/role/link |
| Annexed detailed schedule of corporate bonds and short-term and long-term borrowings-HWY [heading] | en | http://www.xbrl.org/2003/role/verboseLabel | http://www.xbrl.org/2003/role/link |