cm:Member: us-gaap:ChangeInAccountingMethodAccountedForAsChangeInEstimateMember
| Change in Accounting Method Accounted for as Change in Estimate [Member] |
| us-gaap:ChangeInAccountingMethodAccountedForAsChangeInEstimateMember |
| A change from one acceptable accounting method to another based upon a revision in estimated future benefits or obligations. |
| cm:Member |
| [Member] (nonnum:domainItemType) |
| For Period (duration) |
| (no balance type) |
| true |
| us-gaap:ChangeInAccountingMethodAccountedForAsChangeInEstimateMember |