cm:Level3TextBlock: us-gaap:ChangeInClosedBlockAssetsAndLiabilitiesMaximumFutureEarningsToBeRecognizedTableTextBlock
| Change in Closed Block Assets and Liabilities, Maximum Future Earnings to be Recognized [Table Text Block] |
| us-gaap:ChangeInClosedBlockAssetsAndLiabilitiesMaximumFutureEarningsToBeRecognizedTableTextBlock |
| Tabular disclosure of the changes in the maximum future earnings of the closed block. |
| cm:Level3TextBlock |
| Text Block (HTML) (nonnum:textBlockItemType) |
| For Period (duration) |
| (no balance type) |
| false |
| us-gaap:ChangeInClosedBlockAssetsAndLiabilitiesMaximumFutureEarningsToBeRecognizedTableTextBlock |