cm:Concept: us-gaap:IncomeLossFromAffordableHousingProjectsEquityMethodInvestments
| Income (Loss) from Affordable Housing Projects, Equity Method Investments |
| us-gaap:IncomeLossFromAffordableHousingProjectsEquityMethodInvestments |
| Amount of investment income (loss) of qualified affordable housing project investments accounted for using the equity method. |
| cm:Concept |
| Monetary (xbrli:monetaryItemType) |
| For Period (duration) |
| Credit |
| false |
| us-gaap:IncomeLossFromAffordableHousingProjectsEquityMethodInvestments |