| The decrease in regulatory deferral account debit balances resulting from impairments. [Refer: Impairment loss; Regulatory deferral account debit balances] | en | http://www.xbrl.org/2003/role/documentation | http://www.xbrl.org/2003/role/link |
| Decrease through impairments, regulatory deferral account debit balances | en | http://www.xbrl.org/2003/role/label | http://www.xbrl.org/2003/role/link |
| Decrease through impairments, regulatory deferral account debit balances | en | http://www.xbrl.org/2009/role/negatedLabel | http://www.xbrl.org/2003/role/link |