| Standard label: | Deferred Tax Assets, Regulatory Assets and Liabilities |
| Name: | us-gaap:DeferredTaxAssetsRegulatoryAssetsAndLiabilities |
| Documentation: | Amount before allocation of valuation allowances of deferred tax asset attributable to deductible temporary differences derived regulatory assets and liabilities. |
| Object type: | cm:Concept |
| Data type: | Monetary (xbrli:monetaryItemType) |
| Period type: | As Of (instant) |
| Balance type: | Debit |
| Abstract: | false |
| Workiva Wdesk Taxonomy Analyzer: | us-gaap:DeferredTaxAssetsRegulatoryAssetsAndLiabilities |
| Label | Role | Language |
| Deferred Tax Assets, Regulatory Assets and Liabilities | http://www.xbrl.org/2003/role/label | en-US |
| Reference | Role | Topic |
| FASB Accounting Standards Codification 740 10 50 6 | http://fasb.org/us-gaap/role/ref/legacyRef | 740 |
| FASB Accounting Standards Codification 740 10 50 8 | http://fasb.org/us-gaap/role/ref/legacyRef | 740 |
| FASB Accounting Standards Codification 740 10 25 20 | http://fasb.org/us-gaap/role/ref/legacyRef | 740 |
| Part Of Roll Up: |
| us-gaap:DeferredTaxAssetsGross |