cm:Level2TextBlock: us-gaap:FinancingReceivableAllowanceForCreditLossesPolicyForUncollectibleAmounts
| Financing Receivable, Allowance for Credit Losses, Policy for Uncollectible Amounts [Policy Text Block] |
| us-gaap:FinancingReceivableAllowanceForCreditLossesPolicyForUncollectibleAmounts |
| Disclosure of accounting policy for charging off uncollectible financing receivables, including, but not limited to, factors and methodologies used in estimating the allowance for credit loss. |
| cm:Level2TextBlock |
| Text Block (HTML) (nonnum:textBlockItemType) |
| For Period (duration) |
| (no balance type) |
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| us-gaap:FinancingReceivableAllowanceForCreditLossesPolicyForUncollectibleAmounts |