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Common and preferred shares and other equity instruments - Schedule of Common Shares Purchased and Cancelled under Current and Previously Expired NCIB (Detail) - CAD ($) | 12 Months Ended
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Oct. 31, 2025 | Oct. 31, 2024
Disclosure of classes of share capital [line items] |  |
Number of shares | 18,500,000 | 5,000,000
Amount | $ 1,731,000,000 | $ 419,000,000
Number of shares | $ 23,500,000 |
Amount | 2,150,000,000 |
TSX approval date September 5, 2024 [member] |  |
Disclosure of classes of share capital [line items] |  |
Number of shares | 15,000,000 | 5,000,000
Amount | $ 1,338,000,000 | $ 419,000,000
Number of shares | $ 20,000,000 |
Amount | 1,757,000,000 |
TSX approval date September 5, 2025 [member] |  |
Disclosure of classes of share capital [line items] |  |
Number of shares | 3,500,000 |
Amount | $ 393,000,000 |
Number of shares | $ 3,500,000 |
Amount | 393,000,000 |

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- Definition Share repurchase eligible subject to purchase of common shares threshold minimum. + References No definition available. + Details
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Namespace Prefix: | cm_
Data Type: | xbrli:sharesItemType
Balance Type: | na
Period Type: | instant

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- Definition Share repurchase eligible subject to purchase of common shares threshold minimum value. + References No definition available. + Details
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Namespace Prefix: | cm_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

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- Definition Stock repurchased and cancelled during the period shares. + References No definition available. + Details
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- Definition Stock repurchased and cancelled during the period value. + References No definition available. + Details
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Balance Type: | debit
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- Definition Line items represent concepts included in a table. These concepts are used to disclose reportable information associated with members defined in one or many axes of the table. + References No definition available. + Details
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- Details
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Data Type: | na
Balance Type: |
Period Type: |

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- Details
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