cm:Member: us-gaap:FirmCommitmentNotRecognizedAtInceptionFairValueOptionMember
| Firm Commitment Not Recognized at Inception, Fair Value Option [Member] |
| us-gaap:FirmCommitmentNotRecognizedAtInceptionFairValueOptionMember |
| This element represents a firm commitment that would otherwise not be recognized at inception and that involves only financial instruments. For example, a forward purchase contract for a loan that is not readily convertible to cash is a commitment involving only financial instruments-a loan and cash-and would not otherwise be recognized because it is not a derivative instrument. |
| cm:Member |
| [Member] (nonnum:domainItemType) |
| For Period (duration) |
| (no balance type) |
| true |
| us-gaap:FirmCommitmentNotRecognizedAtInceptionFairValueOptionMember |