cm:Level3TextBlock: us-gaap:BusinessCombinationSeparatelyRecognizedTransactionsTableTextBlock
| Business Combination, Separately Recognized Transactions [Table Text Block] |
| us-gaap:BusinessCombinationSeparatelyRecognizedTransactionsTableTextBlock |
| Tabular disclosure of transactions that are recognized separately from the acquisition of assets and assumptions of liabilities in the business combination. |
| cm:Level3TextBlock |
| Text Block (HTML) (nonnum:textBlockItemType) |
| For Period (duration) |
| (no balance type) |
| false |
| us-gaap:BusinessCombinationSeparatelyRecognizedTransactionsTableTextBlock |
| BusinessCombinationSeparatelyRecognizedTransactions |