cm:Concept: us-gaap:InventoryGasInStorageUndergroundNoncurrent
| Inventory, Gas in Storage Underground, Noncurrent |
| us-gaap:InventoryGasInStorageUndergroundNoncurrent |
| Carrying amount as of the balance sheet date of natural gas stored underground in depleted gas reservoirs, aquifers, or salt caverns to meet future seasonal and peak load demands and also as insurance against unforeseen supply disruptions, and deemed to be a noncurrent asset because it is not expected to be used within 12 months or in the normal operating cycle. |
| cm:Concept |
| Monetary (xbrli:monetaryItemType) |
| As Of (instant) |
| Debit |
| false |
| us-gaap:InventoryGasInStorageUndergroundNoncurrent |