cm:Concept: us-gaap:SubsidiaryOrEquityMethodInvesteeCumulativeNumberOfSharesIssuedForAllTransactions
| Subsidiary or Equity Method Investee, Cumulative Number of Shares Issued for All Transactions |
| us-gaap:SubsidiaryOrEquityMethodInvesteeCumulativeNumberOfSharesIssuedForAllTransactions |
| Cumulative number of shares issued or sold by the subsidiary or equity method investee on all stock transactions. |
| cm:Concept |
| Shares (xbrli:sharesItemType) |
| For Period (duration) |
| (no balance type) |
| false |
| us-gaap:SubsidiaryOrEquityMethodInvesteeCumulativeNumberOfSharesIssuedForAllTransactions |