cm:Concept: us-gaap:AvailableForSaleSecuritiesGrossRealizedGainLossNet
| Available-for-sale Securities, Gross Realized Gain (Loss) |
| us-gaap:AvailableForSaleSecuritiesGrossRealizedGainLossNet |
| This item represents the difference between the gross realized gains and losses realized on the sale of debt or equity securities categorized neither as held-to-maturity nor trading securities. Additionally, this item would include any losses recognized for other than temporary impairments (OTTI) of the subject investments in debt and equity securities. |
| cm:Concept |
| Monetary (xbrli:monetaryItemType) |
| For Period (duration) |
| Credit |
| false |
| us-gaap:AvailableForSaleSecuritiesGrossRealizedGainLossNet |