Name:	ima_BusinessCombinationContingentValueRightReceivedForEachShare
Namespace Prefix:	ima_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	duration

The amount of net proceeds, outside of royalties, for potential monetization of legacy programs a contingent value right holder is eligible to receive, as a percentage.

No definition available.

Name:	ima_PercentageOfNetProceedsFromPotentialMonetizationOfLegacyProgramsReceivable
Namespace Prefix:	ima_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	instant

Amount of direct costs of the business combination including legal, accounting, and other costs incurred to consummate the business acquisition.

No definition available.

Name:	us-gaap_BusinessAcquisitionCostOfAcquiredEntityTransactionCosts
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

Number of shares of equity interests issued or issuable to acquire entity.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Topic 805
-SubTopic 30
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (b)(4)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479581/805-30-50-1

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Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	duration

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 805
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 5
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479907/805-20-50-5

Name:	us-gaap_BusinessAcquisitionLineItems
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Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

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Namespace Prefix:
Data Type:	na
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Name:	us-gaap_BusinessAcquisitionAxis=ima_PionyrImmunotherapeuticsIncMember
Namespace Prefix:
Data Type:	na
Balance Type:
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Name:	us-gaap_StatementEquityComponentsAxis=us-gaap_CommonStockMember
Namespace Prefix:
Data Type:	na
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Name:	us-gaap_StatementClassOfStockAxis=us-gaap_NonvotingCommonStockMember
Namespace Prefix:
Data Type:	na
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