| Standard label: | Interest-Only-Strip [Member] |
| Name: | us-gaap:InterestOnlyStripMember |
| Documentation: | Tranche of a securitization that entitles the holder to receive some or all of the interest collected on the underlying mortgages comprising the securitization; a significant risk is prepayment speed greater than the assumption upon which purchase price was based. |
| 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:InterestOnlyStripMember |
| Label | Role | Language |
| Interest-Only-Strip [Member] | http://www.xbrl.org/2003/role/label | en-US |
| Reference | Role | Topic |