cm:Concept: us-gaap:AvailableForSaleSecuritiesEquitySecuritiesNoncurrent
| Available-for-sale Securities, Equity Securities, Noncurrent |
| us-gaap:AvailableForSaleSecuritiesEquitySecuritiesNoncurrent |
| Equity securities categorized neither as held-to-maturity nor trading which are intended be sold more than one year from the balance sheet date or operating cycle, if longer. |
| cm:Concept |
| Monetary (xbrli:monetaryItemType) |
| As Of (instant) |
| Debit |
| false |
| us-gaap:AvailableForSaleSecuritiesEquitySecuritiesNoncurrent |