cm:Concept: us-gaap:DeferredPolicyAcquisitionCostsAndPresentValueOfFutureProfitsAdditions
| Deferred Policy Acquisition Costs and Present Value of Future Insurance Profits, Addition |
| us-gaap:DeferredPolicyAcquisitionCostsAndPresentValueOfFutureProfitsAdditions |
| Amount of addition in deferred policy acquisition costs and present value of future profits from insurance contract acquired in business combination. |
| cm:Concept |
| Monetary (xbrli:monetaryItemType) |
| For Period (duration) |
| Debit |
| false |
| us-gaap:DeferredPolicyAcquisitionCostsAndPresentValueOfFutureProfitsAdditions |