cm:Member: us-gaap:GuaranteeOfScheduledContractualCashFlowsFromAssetsOfSpecialPurposeEntitySPEMember
| Guarantee of Scheduled Contractual Cash Flows from Assets of Transferee [Member] |
| us-gaap:GuaranteeOfScheduledContractualCashFlowsFromAssetsOfSpecialPurposeEntitySPEMember |
| The guarantee of the collection of the scheduled contractual cash flows from individual financial assets held by a transferee. |
| cm:Member |
| [Member] (nonnum:domainItemType) |
| For Period (duration) |
| (no balance type) |
| true |
| us-gaap:GuaranteeOfScheduledContractualCashFlowsFromAssetsOfSpecialPurposeEntitySPEMember |