cm:Concept: us-gaap:EarningsPerSharePotentiallyDilutiveSecurities
| Earnings Per Share, Potentially Dilutive Securities |
| us-gaap:EarningsPerSharePotentiallyDilutiveSecurities |
| Securities (including those issuable pursuant to contingent stock agreements) that could potentially dilute basic earnings per share (EPS) in the future that were not included in the computation of diluted EPS because to do so would have been antidilutive for the period presented. |
| cm:Concept |
| Text/String (xbrli:stringItemType) |
| For Period (duration) |
| (no balance type) |
| false |
| us-gaap:EarningsPerSharePotentiallyDilutiveSecurities |