cm:Concept: us-gaap:PaymentToAcquireLifeInsurancePolicyOperatingActivities
| Payment to Acquire Life Insurance Policy, Operating Activities |
| us-gaap:PaymentToAcquireLifeInsurancePolicyOperatingActivities |
| Amount of cash outflow for payment of premium on corporate-owned life insurance policy, classified as operating activities. Includes, but is not limited to, bank-owned life insurance policy. |
| cm:Concept |
| Monetary (xbrli:monetaryItemType) |
| For Period (duration) |
| Credit |
| false |
| us-gaap:PaymentToAcquireLifeInsurancePolicyOperatingActivities |