cm:Concept: us-gaap:IncrementalCommonSharesAttributableToContingentlyIssuableShares
| Incremental Common Shares Attributable to Dilutive Effect of Contingently Issuable Shares |
| us-gaap:IncrementalCommonSharesAttributableToContingentlyIssuableShares |
| Additional shares included in the calculation of diluted EPS as a result of the potentially dilutive effect of contingently issuable shares. Contingently issuable shares are those shares that are issuable for little or no cash contingent on certain conditions being met. |
| cm:Concept |
| Shares (xbrli:sharesItemType) |
| For Period (duration) |
| (no balance type) |
| false |
| us-gaap:IncrementalCommonSharesAttributableToContingentlyIssuableShares |