cm:Level3TextBlock: us-gaap:ScheduleOfClosedBlockAssetsAndLiabilities
| Schedule of Closed Block Assets and Liabilities [Table Text Block] |
| us-gaap:ScheduleOfClosedBlockAssetsAndLiabilities |
| Tabular disclosure of summarized financial data of the closed block, typically including the liabilities of the closed block, assets allocated thereto, and maximum expected future earnings from the operations thereof. |
| cm:Level3TextBlock |
| Text Block (HTML) (nonnum:textBlockItemType) |
| For Period (duration) |
| (no balance type) |
| false |
| us-gaap:ScheduleOfClosedBlockAssetsAndLiabilities |