cm:Concept: us-gaap:IncreaseDecreaseInReinsuranceRecoverable
| Increase (Decrease) in Reinsurance Recoverable |
| us-gaap:IncreaseDecreaseInReinsuranceRecoverable |
| The increase (decrease) during the reporting period in the amount of benefits the ceding insurer expects to recover on insurance policies ceded to other insurance entities as of the balance sheet date for all guaranteed benefit types. |
| cm:Concept |
| Monetary (xbrli:monetaryItemType) |
| For Period (duration) |
| Credit |
| false |
| us-gaap:IncreaseDecreaseInReinsuranceRecoverable |