Post-Employment Benefits - Summary of Major Categories of Defined Benefit Plan Assets (Detail) - CAD ($) $ in Millions	12 Months Ended
Oct. 31, 2020	Oct. 31, 2019
Disclosure of fair value of plan assets [line items]
Obligations related to securities sold under repurchase agreements	$ 71,653	$ 51,801
Pension plan [member]
Disclosure of fair value of plan assets [line items]
Plan assets	9,341	8,853
Canada plan [member] \| Pension plan [member]
Disclosure of fair value of plan assets [line items]
Canadian equity securities	540	547
Debt securities	6,196	5,723
Investment funds	1,792	1,712
Alternative investments	1,281	1,095
Cash and cash equivalents and other	241	220
Obligations related to securities sold under repurchase agreements	(1,581)	(1,293)
Other	(59)	22
Plan assets	$ 8,469	$ 8,004
Percentage of Canadian equity securities	6.00%	7.00%
Percentage of debt securities	73.00%	72.00%
Percentage of investment funds	21.00%	21.00%
Percentage of alternative investments	16.00%	13.00%
Percentage of cash and cash equivalents and other	3.00%	3.00%
Percentage of Obligations related to securities sold under repurchase agreements	(19.00%)	(16.00%)
Percentage of plan assets	100.00%	100.00%
Canada plan [member] \| Pension plan [member] \| Government bonds [member]
Disclosure of fair value of plan assets [line items]
Debt securities	$ 5,001	$ 4,623
Percentage of debt securities	59.00%	58.00%
Canada plan [member] \| Pension plan [member] \| Corporate Bonds [member]
Disclosure of fair value of plan assets [line items]
Debt securities	$ 1,195	$ 1,024
Percentage of debt securities	14.00%	13.00%
Canada plan [member] \| Pension plan [member] \| Inflation adjusted bonds [member]
Disclosure of fair value of plan assets [line items]
Debt securities		$ 76
Percentage of debt securities		1.00%
Canada plan [member] \| Pension plan [member] \| Canadian equity funds [member]
Disclosure of fair value of plan assets [line items]
Investment funds	$ 30	$ 28
Canada plan [member] \| Pension plan [member] \| US equity funds [member]
Disclosure of fair value of plan assets [line items]
Investment funds	$ 423	$ 379
Percentage of investment funds	5.00%	5.00%
Canada plan [member] \| Pension plan [member] \| International equity funds [member]
Disclosure of fair value of plan assets [line items]
Investment funds	$ 32	$ 32
Canada plan [member] \| Pension plan [member] \| Global equity funds [member]
Disclosure of fair value of plan assets [line items]
Investment funds	$ 961	$ 907
Percentage of investment funds	12.00%	12.00%
Canada plan [member] \| Pension plan [member] \| Emerging markets equity funds [member]
Disclosure of fair value of plan assets [line items]
Investment funds	$ 229	$ 256
Percentage of investment funds	3.00%	3.00%
Canada plan [member] \| Pension plan [member] \| Fixed income funds [member]
Disclosure of fair value of plan assets [line items]
Investment funds	$ 117	$ 110
Percentage of investment funds	1.00%	1.00%

Alternative investment funds amount contributed to fair value of plan assets.

No definition available.

Name:	cm_AlternativeInvestmentFundsAmountContributedToFairValueOfPlanAssets
Namespace Prefix:	cm_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Obligations related to securities sold under repurchase agreements.

+ References

No definition available.

+ Details

Name:	cm_ObligationsRelatedToSecuritiesSoldUnderRepurchaseAgreements
Namespace Prefix:	cm_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Other assets amount contributed to fair value of plan assets net.

+ References

No definition available.

+ Details

Name:	cm_OtherAssetsAmountContributedToFairValueOfPlanAssetsNet
Namespace Prefix:	cm_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Percentage of alternative investment.

+ References

No definition available.

+ Details

Name:	cm_PercentageOfAlternativeInvestment
Namespace Prefix:	cm_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Percentage of Cash and cash equivalents, amount contributed to fair value of plan assets

+ References

No definition available.

+ Details

Name:	cm_PercentageOfCashAndCashEquivalentsAmountContributedToFairValueOfPlanAssets
Namespace Prefix:	cm_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Percentage of debt instruments, amount contributed to fair value of plan assets.

+ References

No definition available.

+ Details

Name:	cm_PercentageOfDebtInstrumentsAmountContributedToFairValueOfPlanAssets
Namespace Prefix:	cm_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Percentage of Equity instruments, amount contributed to fair value of plan assets

+ References

No definition available.

+ Details

Name:	cm_PercentageOfEquityInstrumentsAmountContributedToFairValueOfPlanAssets
Namespace Prefix:	cm_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Percentage of investment funds, amount contributed to fair value of plan assets

+ References

No definition available.

+ Details

Name:	cm_PercentageOfInvestmentFundsAmountContributedToFairValueOfPlanAssets
Namespace Prefix:	cm_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Percentage of Obligations related to securities sold under repurchase agreements.

+ References

No definition available.

+ Details

Name:	cm_PercentageOfObligationsRelatedToSecuritiesSoldUnderRepurchaseAgreements
Namespace Prefix:	cm_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Percentage of plan assets at fair value.

+ References

No definition available.

+ Details

Name:	cm_PercentageOfPlanAssetsAtFairValue
Namespace Prefix:	cm_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

The amount cash and cash equivalents contribute to the fair value of defined benefit plan assets. [Refer: Cash and cash equivalents; Plan assets, at fair value; Defined benefit plans [member]]

+ References

Reference 1: http://www.xbrl.org/2003/role/exampleRef
-Name IAS
-Number 19
-IssueDate 2019-01-01
-Paragraph 142
-Subparagraph a
-URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IAS&num=19&code=ifrs-tx-2019-en-r&anchor=para_142_a&doctype=Standard
-URIDate 2019-03-27

+ Details

Name:	ifrs-full_CashAndCashEquivalentsAmountContributedToFairValueOfPlanAssets
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

The amount instruments representing debt (rather than equity) contribute to the fair value of defined benefit plan assets. [Refer: Plan assets, at fair value; Defined benefit plans [member]]

+ References

Reference 1: http://www.xbrl.org/2003/role/exampleRef
-Name IAS
-Number 19
-IssueDate 2019-01-01
-Paragraph 142
-Subparagraph c
-URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IAS&num=19&code=ifrs-tx-2019-en-r&anchor=para_142_c&doctype=Standard
-URIDate 2019-03-27

+ Details

Name:	ifrs-full_DebtInstrumentsAmountContributedToFairValueOfPlanAssets
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Line items represent concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes of the table.

+ References

No definition available.

+ Details

Name:	ifrs-full_DisclosureOfFairValueOfPlanAssetsLineItems
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

The amount instruments representing equity (rather than debt) contribute to the fair value of defined benefit plan assets. [Refer: Plan assets, at fair value; Defined benefit plans [member]]

+ References

Reference 1: http://www.xbrl.org/2003/role/exampleRef
-Name IAS
-Number 19
-IssueDate 2019-01-01
-Paragraph 142
-Subparagraph b
-URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IAS&num=19&code=ifrs-tx-2019-en-r&anchor=para_142_b&doctype=Standard
-URIDate 2019-03-27

+ Details

Name:	ifrs-full_EquityInstrumentsAmountContributedToFairValueOfPlanAssets
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

The amount investment funds contribute to the fair value of defined benefit plan assets. [Refer: Plan assets, at fair value; Defined benefit plans [member]; Investment funds [member]]

+ References

Reference 1: http://www.xbrl.org/2003/role/exampleRef
-Name IAS
-Number 19
-IssueDate 2019-01-01
-Paragraph 142
-Subparagraph f
-URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IAS&num=19&code=ifrs-tx-2019-en-r&anchor=para_142_f&doctype=Standard
-URIDate 2019-03-27

+ Details

Name:	ifrs-full_InvestmentFundsAmountContributedToFairValueOfPlanAssets
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

The fair value of defined benefit plan assets. Plan assets comprise assets held by a long-term employee benefit fund and qualifying insurance policies. [Refer: At fair value [member]]

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Name IAS
-Number 19
-IssueDate 2019-01-01
-Paragraph 57
-Subparagraph a
-URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IAS&num=19&code=ifrs-tx-2019-en-r&anchor=para_57_a&doctype=Standard
-URIDate 2019-03-27

+ Details

Name:	ifrs-full_PlanAssetsAtFairValue
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Details

Name:	cm_DefinedBenefitPlansByNameAxis=cm_PensionPlanMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	ifrs-full_DefinedBenefitPlansAxis=cm_DomesticDefinedBenefitPlans1Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	ifrs-full_CategoriesOfFinancialAssetsAxis=cm_GovernmentBondsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	ifrs-full_CategoriesOfFinancialAssetsAxis=cm_CorporateBondsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	ifrs-full_CategoriesOfFinancialAssetsAxis=cm_InflationAdjustedBondsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	ifrs-full_CategoriesOfFinancialAssetsAxis=cm_CanadianEquityFundsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	ifrs-full_CategoriesOfFinancialAssetsAxis=cm_USEquityFundsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	ifrs-full_CategoriesOfFinancialAssetsAxis=cm_InternationalEquityFundsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	ifrs-full_CategoriesOfFinancialAssetsAxis=cm_GlobalEquityFundsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	ifrs-full_CategoriesOfFinancialAssetsAxis=cm_EmergingMarketsEquityFundsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	ifrs-full_CategoriesOfFinancialAssetsAxis=cm_FixedIncomeFunds1Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: