Name:	imvt_PercentageOfResearchAndDevelopmentCosts
Namespace Prefix:	imvt_
Data Type:	dtr-types1:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Purchase Obligation, Additional Purchases, Period

+ References

No definition available.

+ Details

Name:	imvt_PurchaseObligationAdditionalPurchasesPeriod
Namespace Prefix:	imvt_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Sub licensed agreement aggregate purchase price.

+ References

No definition available.

+ Details

Name:	imvt_SubLicensedAgreementAggregatePurchasePrice
Namespace Prefix:	imvt_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Upfront payments

+ References

No definition available.

+ Details

Name:	imvt_UpfrontPayments
Namespace Prefix:	imvt_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

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.

+ References

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

Minimum amount of purchase arrangement in which the entity has agreed to expend funds to procure goods or services from a supplier.

+ References

No definition available.

+ Details

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

- Definition

Amount of unrecorded obligation to transfer funds in future for fixed or minimum amount or quantity of product and service at fixed or minimum price. Includes, but is not limited to, lease not yet commenced and take-or-pay and throughput contracts.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 440
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 4
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482648/440-10-50-4

Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 842
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 3
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147478964/842-20-50-3

+ Details

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

- Details

Name:	srt_CounterpartyNameAxis=imvt_SamsungBiologicsCoLtdMember
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:	us-gaap_UnrecordedUnconditionalPurchaseObligationByCategoryOfItemPurchasedAxis=imvt_UponAchievementOfDevelopmentRegulatoryAndSalesMilestonesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Material Agreements (Details) - USD ($) $ in Millions				3 Months Ended
Material Agreements (Details) - USD ($) $ in Millions	Nov. 17, 2021	Dec. 07, 2018	Dec. 19, 2017	Sep. 30, 2023	Dec. 31, 2024
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Upfront, non-refundable payment			$ 30.0
Research and development and out-of-pocket			50.00%
Cumulative milestone payments					$ 32.5
Purchase price		$ 37.8
Acquired in-process research and development				$ 12.5
Samsung Biologics Co., Ltd
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Purchase obligation, additional purchases, period	4 years
Purchase obligation					$ 43.6
Maximum
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Consideration paid			$ 20.0
Maximum \| Upon Achievement Of Development Regulatory And Sales Milestones
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Contingent milestone payments			$ 420.0