cm:Concept: us-gaap:SaleOfStockConsiderationReceivedPerTransaction
| Sale of Stock, Consideration Received Per Transaction |
| us-gaap:SaleOfStockConsiderationReceivedPerTransaction |
| Amount of consideration received by subsidiary or equity investee in exchange for shares of stock issued or sold. Includes amount of cash received, fair value of noncash assets received, and fair value of liabilities assumed by the investor. |
| cm:Concept |
| Monetary (xbrli:monetaryItemType) |
| For Period (duration) |
| Debit |
| false |
| us-gaap:SaleOfStockConsiderationReceivedPerTransaction |