cm:Concept: us-gaap:NetInvestmentInLeaseChangeInPresentValueInterestIncome
| Net Investment in Lease, Change in Present Value, Interest Income |
| us-gaap:NetInvestmentInLeaseChangeInPresentValueInterestIncome |
| Amount of interest income on net investment in sales-type and direct financing leases, from change in present value of expected cash flows, attributable to passage of time. |
| cm:Concept |
| Monetary (xbrli:monetaryItemType) |
| For Period (duration) |
| Credit |
| false |
| us-gaap:NetInvestmentInLeaseChangeInPresentValueInterestIncome |