cm:Concept: us-gaap:AdjustmentsToAdditionalPaidInCapitalDividendsInExcessOfRetainedEarnings
| Adjustments to Additional Paid in Capital, Dividends in Excess of Retained Earnings |
| us-gaap:AdjustmentsToAdditionalPaidInCapitalDividendsInExcessOfRetainedEarnings |
| Amount of decrease in additional paid in capital (APIC) resulting from dividends legally declared (or paid) in excess of retained earnings balance. |
| cm:Concept |
| Monetary (xbrli:monetaryItemType) |
| For Period (duration) |
| Debit |
| false |
| us-gaap:AdjustmentsToAdditionalPaidInCapitalDividendsInExcessOfRetainedEarnings |