cm:Concept: us-gaap:InvestmentOwnedFromCashCollateralReceivedFromInvestmentsOnLoanFlag
| Investment Owned, from Cash Collateral Received from Investment on Loan [true false] |
| us-gaap:InvestmentOwnedFromCashCollateralReceivedFromInvestmentsOnLoanFlag |
| Indicates the investment was purchased with cash collateral received from investments on loan. |
| cm:Concept |
| Yes/No (xbrli:booleanItemType) |
| For Period (duration) |
| (no balance type) |
| false |
| us-gaap:InvestmentOwnedFromCashCollateralReceivedFromInvestmentsOnLoanFlag |