cm:Concept: us-gaap:SalesTypeLeaseNetInvestmentInLeaseChangeInPresentValueInterestIncome
| Sales-type Lease, Net Investment in Lease, Change in Present Value, Interest Income |
| us-gaap:SalesTypeLeaseNetInvestmentInLeaseChangeInPresentValueInterestIncome |
| Amount of interest income on net investment in sales-type lease, 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:SalesTypeLeaseNetInvestmentInLeaseChangeInPresentValueInterestIncome |