cm:Concept: us-gaap:AvailableForSaleSecuritiesTransfersToTradingGrossLosses
| Available-for-sale Securities, Transfers to Trading, Gross Losses |
| us-gaap:AvailableForSaleSecuritiesTransfersToTradingGrossLosses |
| This item represents the gross amount of losses included in earnings from transfers of securities from the available-for-sale category into the trading category. Such losses represent the unrealized losses included in other comprehensive income associated with the securities transferred from the available-for-sale category to the trading category. |
| cm:Concept |
| Monetary (xbrli:monetaryItemType) |
| For Period (duration) |
| Debit |
| false |
| us-gaap:AvailableForSaleSecuritiesTransfersToTradingGrossLosses |