cm:Concept: us-gaap:NetChangeAnnuitiesAndInvestmentCertificates
| Net Change Annuities and Investment Certificates |
| us-gaap:NetChangeAnnuitiesAndInvestmentCertificates |
| The cash inflow or outflow for an insurance contract under which the policy holder make a lump sum payment or a series of payments in exchange for periodic payments to the policyholder beginning immediately or at some future date. |
| cm:Concept |
| Monetary (xbrli:monetaryItemType) |
| For Period (duration) |
| Debit |
| false |
| us-gaap:NetChangeAnnuitiesAndInvestmentCertificates |