cm:Level2TextBlock: us-gaap:InsurancePremiumsRevenueRecognitionPolicy
| Insurance Premiums Revenue Recognition, Policy [Policy Text Block] |
| us-gaap:InsurancePremiumsRevenueRecognitionPolicy |
| Disclosure of accounting policy for revenue recognition of insurance premium. Includes, but is not limited to, basis for measurement and timing of recognition of revenue from insurance premium received from contract holder and method used in performing premium deficiency testing. |
| cm:Level2TextBlock |
| Text Block (HTML) (nonnum:textBlockItemType) |
| For Period (duration) |
| (no balance type) |
| false |
| us-gaap:InsurancePremiumsRevenueRecognitionPolicy |