cm:Concept: us-gaap:PublicUtilitiesNatureOfAllowanceForEarningsOnEquityCapitalizedForRateMakingPurposes
| Public Utilities, Nature of Allowance for Earnings on Equity Capitalized for Rate Making Purposes |
| us-gaap:PublicUtilitiesNatureOfAllowanceForEarningsOnEquityCapitalizedForRateMakingPurposes |
| Description of the nature of any allowance for earnings on shareholders' equity capitalized for rate making purposes but not for the financial statements. |
| cm:Concept |
| Text/String (xbrli:stringItemType) |
| For Period (duration) |
| (no balance type) |
| false |
| us-gaap:PublicUtilitiesNatureOfAllowanceForEarningsOnEquityCapitalizedForRateMakingPurposes |