cm:Concept: us-gaap:BusinessCombinationSeparatelyRecognizedTransactionsRevenuesAndGainsRecognized
| Business Combination, Separately Recognized Transactions, Revenues and Gains Recognized |
| us-gaap:BusinessCombinationSeparatelyRecognizedTransactionsRevenuesAndGainsRecognized |
| The revenues and gains recognized recorded for each transaction with the acquiree that is recognized separately from the acquisition of assets and assumptions of liabilities in the business combination. |
| cm:Concept |
| Monetary (xbrli:monetaryItemType) |
| For Period (duration) |
| Credit |
| false |
| us-gaap:BusinessCombinationSeparatelyRecognizedTransactionsRevenuesAndGainsRecognized |