cm:Concept: us-gaap:RestrictedStockSharesIssuedNetOfSharesForTaxWithholdings
| Restricted Stock, Shares Issued Net of Shares for Tax Withholdings |
| us-gaap:RestrictedStockSharesIssuedNetOfSharesForTaxWithholdings |
| Number, after shares used to satisfy grantee's tax withholding obligation for award under share-based payment arrangement, of restricted shares issued. Excludes cash used to satisfy grantee's tax withholding obligation. |
| cm:Concept |
| Shares (xbrli:sharesItemType) |
| For Period (duration) |
| (no balance type) |
| false |
| us-gaap:RestrictedStockSharesIssuedNetOfSharesForTaxWithholdings |