cm:Concept: us-gaap:FairValueLiabilitiesMeasuredOnRecurringBasisSubordinatedDebtObligations
| Subordinated Debt Obligations, Fair Value Disclosure |
| us-gaap:FairValueLiabilitiesMeasuredOnRecurringBasisSubordinatedDebtObligations |
| Fair value of subordinated debt obligations including, but not limited to, subordinated loan, subordinated bond, subordinated debenture or junior debt. |
| cm:Concept |
| Monetary (xbrli:monetaryItemType) |
| As Of (instant) |
| Credit |
| false |
| us-gaap:FairValueLiabilitiesMeasuredOnRecurringBasisSubordinatedDebtObligations |