cm:Concept: us-gaap:SubsidiaryOrEquityMethodInvesteeCumulativePercentageOwnershipAfterAllTransactions
| Subsidiary or Equity Method Investee, Cumulative Percentage Ownership after All Transactions |
| us-gaap:SubsidiaryOrEquityMethodInvesteeCumulativePercentageOwnershipAfterAllTransactions |
| Percentage of subsidiary's or equity method investee's stock owned by parent immediately after all stock transactions. |
| cm:Concept |
| Percent (num:percentItemType) |
| For Period (duration) |
| (no balance type) |
| false |
| us-gaap:SubsidiaryOrEquityMethodInvesteeCumulativePercentageOwnershipAfterAllTransactions |