cm:Level3TextBlock: us-gaap:LiabilityForFuturePolicyBenefitActivityTableTextBlock
| Liability for Future Policy Benefit, Activity [Table Text Block] |
| us-gaap:LiabilityForFuturePolicyBenefitActivityTableTextBlock |
| Tabular disclosure of beginning balance to ending balance for liability for future policy benefit, with separate presentation of expected future net premium and expected future benefit. |
| cm:Level3TextBlock |
| Text Block (HTML) (nonnum:textBlockItemType) |
| For Period (duration) |
| (no balance type) |
| false |
| us-gaap:LiabilityForFuturePolicyBenefitActivityTableTextBlock |