cm:Concept: us-gaap:FairValueOptionAggregateDifferencesLoansAndLongTermReceivables
| Fair Value, Option, Aggregate Differences, Loans and Long-term Receivables |
| us-gaap:FairValueOptionAggregateDifferencesLoansAndLongTermReceivables |
| This item represents the difference between the aggregate fair value and the aggregate unpaid principal balance of loans and long-term receivables (other than securities categorized as trading, available-for-sale or held-to-maturity) that have contractual principal amounts and for which the fair value option has been elected. |
| cm:Concept |
| Monetary (xbrli:monetaryItemType) |
| As Of (instant) |
| Debit |
| false |
| us-gaap:FairValueOptionAggregateDifferencesLoansAndLongTermReceivables |