| Standard label: | Schedule of Guarantor Obligations [Table Text Block] |
| Name: | us-gaap:ScheduleOfGuaranteeObligationsTextBlock |
| Documentation: | Tabular disclosure of each guarantee obligation, or each group of similar guarantee obligations, including (a) the nature of the guarantee, including its term, how it arose, and the events or circumstances that would require the guarantor to perform under the guarantee; (b) the maximum potential amount of future payments (undiscounted) the guarantor could be required to make under the guarantee; (c) the current carrying amount of the liability, if any, for the guarantor's obligations under the guarantee; and (d) the nature of any recourse provisions under the guarantee, and any assets held either as collateral or by third parties, and any relevant related party disclosure. Excludes disclosures about product warranties. |
| Object type: | cm:Level3TextBlock |
| Data type: | Text Block (HTML) (nonnum:textBlockItemType) |
| Period type: | For Period (duration) |
| Balance type: | (no balance type) |
| Abstract: | false |
| Workiva Wdesk Taxonomy Analyzer: | us-gaap:ScheduleOfGuaranteeObligationsTextBlock |
| Examples of this text block disclosure: | GuarantorObligations |
| Label | Role | Language |
| Schedule of Guarantor Obligations [Table Text Block] | http://www.xbrl.org/2003/role/label | en-US |
| Reference | Role | Topic |
| FASB Accounting Standards Codification 460 10 50 4 | http://fasb.org/us-gaap/role/ref/legacyRef | 460 |
| FASB Accounting Standards Codification 460 10 50 6 | http://fasb.org/us-gaap/role/ref/legacyRef | 460 |