cm:Level1TextBlock: us-gaap:RepurchaseAgreementsResaleAgreementsSecuritiesBorrowedAndSecuritiesLoanedDisclosureTextBlock
| Repurchase Agreements, Resale Agreements, Securities Borrowed, and Securities Loaned Disclosure [Text Block] |
| us-gaap:RepurchaseAgreementsResaleAgreementsSecuritiesBorrowedAndSecuritiesLoanedDisclosureTextBlock |
| The entire disclosure for repurchase agreements (also known as repos), resale agreements (also known as reverse repurchase agreements or reverse repos), securities borrowed transactions, and securities loaned transactions. |
| cm:Level1TextBlock |
| Text Block (HTML) (nonnum:textBlockItemType) |
| For Period (duration) |
| (no balance type) |
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| us-gaap:RepurchaseAgreementsResaleAgreementsSecuritiesBorrowedAndSecuritiesLoanedDisclosureTextBlock |