| Standard label: | Common Stock Subject to Mandatory Redemption [Member] |
| Name: | us-gaap:CommonStockSubjectToMandatoryRedemptionMember |
| Documentation: | Shares that embody an unconditional obligation requiring the issuer to redeem the securities by transferring the assets at a specified or determinable date (or dates) or upon an event that is certain to occur, that represent equity ownership in a corporation, provide voting rights, entitle the holder to a share of the company's success through dividends and/or capital appreciation and, in the event of liquidation, provide rights to a company's assets only after bondholders, other debt holders, and preferred stockholders have been satisfied. |
| Object type: | cm:Member |
| Data type: | [Member] (nonnum:domainItemType) |
| Period type: | For Period (duration) |
| Balance type: | (no balance type) |
| Abstract: | true |
| Workiva Wdesk Taxonomy Analyzer: | us-gaap:CommonStockSubjectToMandatoryRedemptionMember |
| Label | Role | Language |
| Common Stock Subject to Mandatory Redemption [Member] | http://www.xbrl.org/2003/role/label | en-US |
| Reference | Role | Topic |
| FASB Accounting Standards Codification 480 10 50 1 | http://fasb.org/us-gaap/role/ref/legacyRef | 480 |
| FASB Accounting Standards Codification 480 10 50 2 | http://fasb.org/us-gaap/role/ref/legacyRef | 480 |