cm:Concept: us-gaap:DecommissioningTrustAssetsAmount
| Decommissioning Fund Investments, Fair Value |
| us-gaap:DecommissioningTrustAssetsAmount |
| The fair value of investments held in a trust fund to pay for the costs of decontaminating and decommissioning facilities, whether such amount is presented as a separate caption or as a parenthetical disclosure on the balance sheet. Additionally, this element may be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements. |
| cm:Concept |
| Monetary (xbrli:monetaryItemType) |
| As Of (instant) |
| Debit |
| false |
| us-gaap:DecommissioningTrustAssetsAmount |