| Remaining recovery period of regulatory deferral account debit balances | en | http://www.xbrl.org/2003/role/label | http://www.xbrl.org/2003/role/link |
| Concept not required as a result of 2018 annual improvements | en | http://www.xbrl.org/2009/role/deprecatedLabel | http://www.xbrl.org/2003/role/link |
| 2019-01-01 | en | http://www.xbrl.org/2009/role/deprecatedDateLabel | http://www.xbrl.org/2003/role/link |
| The remaining recovery period of regulatory deferral account debit balances. [Refer: Regulatory deferral account debit balances] | en | http://www.xbrl.org/2003/role/documentation | http://www.xbrl.org/2003/role/link |