cm:Level3TextBlock: us-gaap:ScheduleOfResaleAgreementCounterpartiesWithWhomResaleAgreementsExceed10PercentOfStockholdersEquityTextBlock
| Schedule of Resale Agreement Counterparties with Whom Resale Agreements Exceed 10 Percent of Stockholders' Equity [Table Text Block] |
| us-gaap:ScheduleOfResaleAgreementCounterpartiesWithWhomResaleAgreementsExceed10PercentOfStockholdersEquityTextBlock |
| Tabular disclosure, as of the most recent balance sheet date, of the amount at risk under resale agreements (reverse repurchase agreements) with any individual counterparty or group of related counterparties that exceeds 10 percent of stockholders' equity. Disclosure may include: the name of each such counterparty or group of related counterparties, the amount at risk with each, and the weighted average maturity of the resale agreements with each. The amount at risk under resale agreements is defined as the excess of carrying amount over market value of assets delivered pursuant to the agreements by the counterparty to the registrant (or to a third party agent that has affirmatively agreed to act on behalf of the registrant) and not returned to the counterparty, except in exchange for their approximate market value in a separate transaction. |
| cm:Level3TextBlock |
| Text Block (HTML) (nonnum:textBlockItemType) |
| For Period (duration) |
| (no balance type) |
| false |
| us-gaap:ScheduleOfResaleAgreementCounterpartiesWithWhomResaleAgreementsExceed10PercentOfStockholdersEquityTextBlock |