cm:Concept: us-gaap:ClosedBlockOperationsIncomeLossFromDiscontinuedOperationsNetOfTax
| Closed Block Operations, Income (Loss) from Discontinued Operations, Net of Tax |
| us-gaap:ClosedBlockOperationsIncomeLossFromDiscontinuedOperationsNetOfTax |
| Amount after tax of income (loss) from a disposal group, which is allocated to the operations of the closed block. |
| cm:Concept |
| Monetary (xbrli:monetaryItemType) |
| For Period (duration) |
| Credit |
| false |
| us-gaap:ClosedBlockOperationsIncomeLossFromDiscontinuedOperationsNetOfTax |