cm:Level2TextBlock: us-gaap:ContractualAdjustmentsAndThirdPartySettlementsPolicyPolicyTextBlock
| Contractual Adjustments and Third Party Settlements, Policy [Policy Text Block] |
| us-gaap:ContractualAdjustmentsAndThirdPartySettlementsPolicyPolicyTextBlock |
| Disclosure of accounting policy for contractual adjustments and third-party settlements. |
| cm:Level2TextBlock |
| Text Block (HTML) (nonnum:textBlockItemType) |
| For Period (duration) |
| (no balance type) |
| false |
| us-gaap:ContractualAdjustmentsAndThirdPartySettlementsPolicyPolicyTextBlock |