| Standard label: | Regulatory Asset [Axis] |
| Name: | us-gaap:RegulatoryAssetAxis |
| Documentation: | Information by type of regulatory asset. |
| Object type: | cm:Axis |
| Data type: | Text/String (xbrli:stringItemType) |
| Period type: | For Period (duration) |
| Balance type: | (no balance type) |
| Abstract: | true |
| Workiva Wdesk Taxonomy Analyzer: | us-gaap:RegulatoryAssetAxis |
| Label | Role | Language |
| Regulatory Asset [Axis] | http://www.xbrl.org/2003/role/label | en-US |
| Reference | Role | Topic |
| FASB Accounting Standards Codification 980 340 50 1 | http://fasb.org/us-gaap/role/ref/legacyRef | 980 |
| FASB Accounting Standards Codification 980 340 50 2 | http://fasb.org/us-gaap/role/ref/legacyRef | 980 |
| FASB Accounting Standards Codification 980 715 50 1 | http://fasb.org/us-gaap/role/ref/legacyRef | 980 |