cm:Concept: us-gaap:QuarterlyFinancialInformationQuarterlyChargesAndCreditsAmountReconcilingToPreviouslyReportedResults
| Quarterly Financial Information, Quarterly Charges and Credits, Amount Reconciling to Previously Reported Results |
| us-gaap:QuarterlyFinancialInformationQuarterlyChargesAndCreditsAmountReconcilingToPreviouslyReportedResults |
| Amount by which previously reported quarterly results were revised (for example, to correct an error, or to give retrospective effect to a change in an accounting principle). |
| cm:Concept |
| Monetary (xbrli:monetaryItemType) |
| For Period (duration) |
| Debit |
| false |
| us-gaap:QuarterlyFinancialInformationQuarterlyChargesAndCreditsAmountReconcilingToPreviouslyReportedResults |