| Standard label: | Equity Method Investments [Policy Text Block] |
| Name: | us-gaap:EquityMethodInvestmentsPolicy |
| Documentation: | Disclosure of accounting policy for equity method of accounting for investments and other interests. Investment includes, but is not limited to, unconsolidated subsidiary, corporate joint venture, noncontrolling interest in real estate venture, limited partnership, and limited liability company. Information includes, but is not limited to, ownership percentage, reason equity method is or is not considered appropriate, and accounting policy election for distribution received. |
| Object type: | cm:Level2TextBlock |
| 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:EquityMethodInvestmentsPolicy |
| Label | Role | Language |
| Equity Method Investments [Policy Text Block] | http://www.xbrl.org/2003/role/label | en-US |
| Reference | Role | Topic |
| FASB Accounting Standards Codification 210 10 S99 1 (SX 210.5-02.12) | http://fasb.org/us-gaap/role/ref/legacyRef | 210 |
| FASB Accounting Standards Codification 230 10 45 21D | http://fasb.org/us-gaap/role/ref/legacyRef | 230 |
| FASB Accounting Standards Codification 235 10 50 3 | http://fasb.org/us-gaap/role/ref/legacyRef | 235 |
| FASB Accounting Standards Codification 323 10 50 3 (a)(2) | http://fasb.org/us-gaap/role/ref/legacyRef | 323 |
| FASB Accounting Standards Codification 825 10 50 28 (f) | http://fasb.org/us-gaap/role/ref/legacyRef | 825 |