cm:Level2TextBlock: us-gaap:EquitySecuritiesWithoutReadilyDeterminableFairValuePolicyTextBlock
| Equity Securities without Readily Determinable Fair Value [Policy Text Block] |
| us-gaap:EquitySecuritiesWithoutReadilyDeterminableFairValuePolicyTextBlock |
| Disclosure of accounting policy for investment in equity security without readily determinable fair value, which does not qualify for practical expedient to estimate fair value using net asset value per share. Includes, but is not limited to, information considered for determining upward and downward adjustment from observable price change. |
| cm:Level2TextBlock |
| Text Block (HTML) (nonnum:textBlockItemType) |
| For Period (duration) |
| (no balance type) |
| false |
| us-gaap:EquitySecuritiesWithoutReadilyDeterminableFairValuePolicyTextBlock |