cm:Concept: us-gaap:SubsidiaryOrEquityMethodInvesteeMinorityInterestInIncomeOfSubsidiary
| Subsidiary or Equity Method Investee, Noncontrolling Interest in Income of Subsidiary |
| us-gaap:SubsidiaryOrEquityMethodInvesteeMinorityInterestInIncomeOfSubsidiary |
| The dividends from redeemable preferred stock of a subsidiary that are accounted for as a noncontrolling interest in income of a subsidiary in a parent's consolidated financial statements. |
| cm:Concept |
| Monetary (xbrli:monetaryItemType) |
| For Period (duration) |
| Debit |
| false |
| us-gaap:SubsidiaryOrEquityMethodInvesteeMinorityInterestInIncomeOfSubsidiary |