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

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 808
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (d)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479402/808-10-50-1

+ Details

Name:	us-gaap_CollaborativeArrangementsAndNoncollaborativeArrangementTransactionsLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

The minimum amount the entity agreed to spend under the long-term purchase commitment.

+ References

No definition available.

+ Details

Name:	us-gaap_LongTermPurchaseCommitmentAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Amount of expenses for non refundable up front payment for license agreement.

+ References

No definition available.

+ Details

Name:	vstm_LicenseAndCollaborationAgreementUpfrontPayment
Namespace Prefix:	vstm_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

The amount paid upon achievement of development milestones.

+ References

No definition available.

+ Details

Name:	vstm_LicenseAndCollaborationAgreementsDevelopmentMilestonePayments
Namespace Prefix:	vstm_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

The number days of written notice from either party to the agreement to terminate agreement for the other party's material breach if such party fails to cure the breach.

+ References

No definition available.

+ Details

Name:	vstm_NumberOfDaysOfPriorNoticeTerminationFailsToCureBreach
Namespace Prefix:	vstm_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

The number days of prior written notice to terminate the agreement.

+ References

No definition available.

+ Details

Name:	vstm_NumberOfDaysOfPriorNoticeToTerminateAgreement.
Namespace Prefix:	vstm_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

The amount of milestone payments the Company may make.

+ References

No definition available.

+ Details

Name:	vstm_PotentialMilestonePayments
Namespace Prefix:	vstm_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Details

Name:	us-gaap_TypeOfArrangementAxis=vstm_LicenseAndCollaborationAgreementMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_CounterpartyNameAxis=vstm_GenfleetTherapeuticsShanghaiIncMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_StatementOfIncomeLocationBalanceAxis=us-gaap_ResearchAndDevelopmentExpense
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_RangeAxis=srt_MaximumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_StatementScenarioAxis=vstm_AchievementOfCertainDevelopmentAndCommercializationMilestonesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_StatementScenarioAxis=vstm_AchievementOfCertainSalesMilestonesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_StatementScenarioAxis=vstm_ExerciseOfAllThreeGenFleetOptionsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_LongTermPurchaseCommitmentByCategoryOfItemPurchasedAxis=us-gaap_ResearchAndDevelopmentArrangementMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

License, collaboration and commercial agreements - Genfleet Therapeutics (Details) - License and Collaboration Agreement - Genfleet - USD ($) $ in Millions		1 Months Ended	12 Months Ended
	Aug. 24, 2023	Jan. 31, 2025	Dec. 31, 2024
License, collaboration and commercial agreements
Upfront payment	$ 2.0
Potential milestone payments	$ 622.0
Payment for development milestone		$ 6.0	$ 3.0
Number of days written prior notice required for other party to terminate agreement	90 days
Number of days written notice required to terminate agreement if fails to cure breach	60 days
Location, Statement of Income, Balance [Axis]: us-gaap:ResearchAndDevelopmentExpense
License, collaboration and commercial agreements
Upfront payment		$ 6.0
Maximum \| Achievement of certain development and commercialization milestones
License, collaboration and commercial agreements
Potential milestone payments	$ 154.0
Maximum \| Achievement of certain sales milestones
License, collaboration and commercial agreements
Potential milestone payments	450.0
Maximum \| Exercise of All Three Gen Fleet Options
License, collaboration and commercial agreements
Potential milestone payments	18.0
Research and Development Arrangement
License, collaboration and commercial agreements
Genfleet R&D Support Fee	$ 1.5