cm:Concept: us-gaap:InterestAndFeeIncomeNonmortgageLoansAndLeasesHeldForSale
| Interest and Fee Income, Nonmortgage Loans and Leases Held-for-sale |
| us-gaap:InterestAndFeeIncomeNonmortgageLoansAndLeasesHeldForSale |
| Amount of interest and fee income earned from loans held-for-sale, including interest earned from direct financing and sales-type leases held-for-sale, but excluding mortgage loans held-for sale. |
| cm:Concept |
| Monetary (xbrli:monetaryItemType) |
| For Period (duration) |
| Credit |
| false |
| us-gaap:InterestAndFeeIncomeNonmortgageLoansAndLeasesHeldForSale |