Percentage points added to the reference rate to compute the variable rate on the debt instrument.

No definition available.

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- Definition

Description of minimum financial levels (for example, tangible net worth and working capital) and achievement of certain financial ratios (for example, working capital ratio and debt service coverage ratio), and adherence to certain clauses which generally require or restrict certain actions (for example, entering into a debt arrangement with equal or greater seniority, and selling or discontinuing a certain business segment or material subsidiary) to be in compliance with the covenant clauses of the debt agreement. May also include a discussion of the adverse consequences that would result if the entity violates or fails to satisfy the covenants.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
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Balance Type:	na
Period Type:	duration

- Definition

Face (par) amount of debt instrument at time of issuance.

+ References

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Contractual interest rate for funds borrowed, under the debt agreement.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 942
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+ Details

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Namespace Prefix:	us-gaap_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Indicates type of variable interest rate on debt instrument.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 942
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-Section 50
-Paragraph 3
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- Definition

Amount of gain (loss) recognized in other comprehensive income (OCI) from liability measured at fair value on recurring basis using unobservable input (level 3).

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 820
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Period Type:	duration

- Definition

Indicates line item in statement in which other comprehensive income (OCI) is reported that includes gain (loss) from liability measured at fair value using unobservable input (level 3).

+ References

+ Details

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Data Type:	enum2:enumerationSetItemType
Balance Type:	na
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- Definition

Maximum borrowing capacity under the credit facility without consideration of any current restrictions on the amount that could be borrowed or the amounts currently outstanding under the facility.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 210
-SubTopic 10
-Name Accounting Standards Codification
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- Definition

Detail information of subsequent event by type. User is expected to use existing line items from elsewhere in the taxonomy as the primary line items for this disclosure, which is further associated with dimension and member elements pertaining to a subsequent event.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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- Definition

Percentage of additional interest rate at the event of default.

+ References

No definition available.

+ Details

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Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Payment made by the company should certain requirements not be met.

+ References

No definition available.

+ Details

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Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Percentage of additional interest rate for notes issued.

+ References

No definition available.

+ Details

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Namespace Prefix:	vstm_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Amount of an additional issue of notes.

+ References

No definition available.

+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Number of equal installments.

+ References

No definition available.

+ Details

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Namespace Prefix:	vstm_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- Definition

The amount of debt issuance costs incurred.

+ References

No definition available.

+ Details

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

- Definition

The amount of threshold sale revenue to be achieved in order for the company to receive the sales milestone payments under the License and collaboration agreements.

+ References

No definition available.

+ Details

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

- Definition

Represents the number of tranches.

+ References

No definition available.

+ Details

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Namespace Prefix:	vstm_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

- Definition

Percentage of participation in net sales of the company.

+ References

No definition available.

+ Details

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Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Percentage of revenue of net sales as payment to purchasers of notes.

+ References

No definition available.

+ Details

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Namespace Prefix:	vstm_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

The total revenue payments to total purchase price ratio.

+ References

No definition available.

+ Details

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- Details

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- Details

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Subsequent events - Third Amendment to Note Purchase Agreement (Details) - Notes $ in Thousands			6 Months Ended		18 Months Ended
	Aug. 06, 2026 USD ($) tranche	Jan. 13, 2025 USD ($) installment	Jun. 30, 2026 USD ($)	Jun. 30, 2025 USD ($)	Jun. 30, 2026 USD ($)
Subsequent events
Aggregate principal amount			$ 75,000		$ 75,000
Additional issue of principal amount of notes		$ 50,000
Debt Instrument, Variable Interest Rate, Type [Extensible Enumeration]		us-gaap:SecuredOvernightFinancingRateSofrMember
Variable rate (as a percent)		4.29%
Additional interest rate (%)		3.71%
Interest rate (as a percent)		9.75%
Additional increase in interest rate at event of default		5.00%
Number of equal installments \| installment		2
Financial covenants		The Note Purchase Agreement contains no financial covenants.
Change in fair value reported in comprehensive loss			$ (2,814)	$ (5,300)	$ (8,000)
Fair Value, Liability, Recurring Basis, Unobservable Input Reconciliation, Liability, Gain (Loss), Statement of Other Comprehensive Income or Comprehensive Income [Extensible Enumeration]			Fair Value Adjustment of Notes, Instrument Specific Credit Risk
Debt issuance costs			$ 700
Maximum
Subsequent events
Aggregate principal amount of notes		$ 150,000
Initial sale
Subsequent events
Aggregate principal amount		75,000
Second sale
Subsequent events
Additional issue of principal amount of notes		$ 25,000
Subsequent events
Subsequent events
Number of tranches \| tranche	2
Aggregate principal amount of notes	$ 75,000
Participation Percentage	1.00%
Total Revenue Payments to Total Purchase Price Ratio	100.00%
Contingent Make Whole Payment of the Funded Amount	100.00%
Subsequent events \| Minimum
Subsequent events
Revenue Payment Percentage	1.75%
Subsequent events \| Maximum
Subsequent events
Revenue Payment Percentage	4.50%
Subsequent events \| Initial sale
Subsequent events
Additional issue of principal amount of notes	$ 50,000
Subsequent events \| Second sale
Subsequent events
Additional issue of principal amount of notes	25,000
Threshold sales to trigger milestone payments	$ 40,000