cm:Member: us-gaap:GovernmentNationalMortgageAssociationCertificatesAndObligationsGNMAMember
| Government National Mortgage Association Certificates and Obligations (GNMA) [Member] |
| us-gaap:GovernmentNationalMortgageAssociationCertificatesAndObligationsGNMAMember |
| Investments in debentures, bonds and other debt securities issued by the Government National Mortgage Association (GNMA or Ginnie Mae). |
| cm:Member |
| [Member] (nonnum:domainItemType) |
| For Period (duration) |
| (no balance type) |
| true |
| us-gaap:GovernmentNationalMortgageAssociationCertificatesAndObligationsGNMAMember |