cm:Axis: us-gaap:BusinessCombinationSeparatelyRecognizedTransactionsAxis
| Business Combination, Separately Recognized Transactions [Axis] |
| us-gaap:BusinessCombinationSeparatelyRecognizedTransactionsAxis |
| Disclosures related to transactions that are recognized separately from the acquisition of assets and assumptions of liabilities in the business combination by type of transaction. |
| cm:Axis |
| Text/String (xbrli:stringItemType) |
| For Period (duration) |
| (no balance type) |
| true |
| us-gaap:BusinessCombinationSeparatelyRecognizedTransactionsAxis |