Anticipated initial collaboration term.

No definition available.

Name:	idra_AnticipatedInitialCollaborationTerm
Namespace Prefix:	idra_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

The percentage of common stock ownership under the collaboration agreement.

+ References

No definition available.

+ Details

Name:	idra_CommonStockOwnershipPercentage
Namespace Prefix:	idra_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Deferred Revenue Recognition Period

+ References

No definition available.

+ Details

Name:	idra_DeferredRevenueRecognitionPeriod
Namespace Prefix:	idra_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Number of optional additional targets.

+ References

No definition available.

+ Details

Name:	idra_NumberOfAdditionalTargetOptional
Namespace Prefix:	idra_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- Definition

The number of board director seats held.

+ References

No definition available.

+ Details

Name:	idra_NumberOfBoardOfDirectorSeatsHeld
Namespace Prefix:	idra_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- Definition

The number of clinical studies conducted.

+ References

No definition available.

+ Details

Name:	idra_NumberOfClinicalStudies
Namespace Prefix:	idra_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- Definition

The number of common board of directors.

+ References

No definition available.

+ Details

Name:	idra_NumberOfCommonBoardOfDirectors
Namespace Prefix:	idra_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- Definition

The number of development candidates.

+ References

No definition available.

+ Details

Name:	idra_NumberOfDevelopmentCandidates
Namespace Prefix:	idra_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- Definition

Maximum royalty percentage on net sales.

+ References

No definition available.

+ Details

Name:	idra_PercentageOfMaximumRoyaltyOnNetSales
Namespace Prefix:	idra_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

The remaining performance obligations under the agreement

+ References

No definition available.

+ Details

Name:	idra_RemainingPerformanceObligations
Namespace Prefix:	idra_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Milestone payments that may be received under collaboration agreements.

+ References

No definition available.

+ Details

Name:	idra_RevenueRecognitionMilestoneMethodMaximumMilestonePayments
Namespace Prefix:	idra_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

The revised, increased research period.

+ References

No definition available.

+ Details

Name:	idra_RevisedResearchAgreementTerm
Namespace Prefix:	idra_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

The total number of board director seats.

+ References

No definition available.

+ Details

Name:	idra_TotalNumberOfBoardOfDirectorSeats
Namespace Prefix:	idra_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- Definition

The upfront, non-refundable, non-creditable cash payment received under the collaboration agreement.

+ References

No definition available.

+ Details

Name:	idra_UpfrontPaymentReceivedUnderCollaboration
Namespace Prefix:	idra_
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

No definition available.

+ Details

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

- Definition

Amount of obligation to transfer good or service to customer for which consideration has been received or is receivable, classified as current.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=82913815&loc=SL49130532-203044

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 45
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=82913815&loc=SL49130531-203044

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 8
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=109196051&loc=SL49130549-203045

+ Details

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

- Details

Name:	us-gaap_RelatedPartyTransactionsByRelatedPartyAxis=idra_BakerBrosAdvisorsLpMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

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

- Details

Name:	us-gaap_TypeOfArrangementAxis=idra_UpFrontPaymentsArrangementMember
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:	idra_PharmaceuticalBackupCompoundsAxis=idra_BackupCompoundMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

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

- Details

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

- Details

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

- Details

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

- Details

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

- Details

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

- Details

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

- Details

Name:	idra_AccountingUnitsAxis=idra_RAndDServicesUnitOfAccountingMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Collaboration and License Agreements (Details) $ in Thousands	1 Months Ended		9 Months Ended
	Nov. 30, 2016 USD ($) director	Nov. 30, 2015 USD ($) person	Sep. 30, 2018 USD ($) item	Dec. 31, 2017 USD ($)
Collaborative Arrangements and Non-collaborative Arrangement Transactions
Contract with Customer, Liability, Current			$ 94	$ 566
Total number of board of director seats \| director	7
Number of common board of directors \| director	0
Baker Bros. Advisors LP
Collaborative Arrangements and Non-collaborative Arrangement Transactions
Common stock ownership percentage under the collaboration agreement	7.00%
Number of board director seats held \| director	2
Vivelix
Collaborative Arrangements and Non-collaborative Arrangement Transactions
Remaining performance obligation			$ 0
Total number of board of director seats \| director	4
Number of clinical studies conducted \| item			2
Vivelix \| Up-front Payment Arrangement
Collaborative Arrangements and Non-collaborative Arrangement Transactions
Upfront payment received under collaboration agreement	$ 15,000
Vivelix \| Maximum
Collaborative Arrangements and Non-collaborative Arrangement Transactions
Milestone payments	$ 140,000
Vivelix \| Maximum \| Back-up compounds
Collaborative Arrangements and Non-collaborative Arrangement Transactions
Anticipated initial collaboration term	3 years
Milestone payments	$ 52,500
Vivelix \| Maximum \| Development and Regulatory Milestones
Collaborative Arrangements and Non-collaborative Arrangement Transactions
Milestone payments	65,000
Vivelix \| Maximum \| Development and Regulatory Milestones \| Back-up compounds
Collaborative Arrangements and Non-collaborative Arrangement Transactions
Milestone payments	35,000
Vivelix \| Maximum \| Sales Milestones
Collaborative Arrangements and Non-collaborative Arrangement Transactions
Milestone payments	75,000
Vivelix \| Maximum \| Sales Milestones \| Back-up compounds
Collaborative Arrangements and Non-collaborative Arrangement Transactions
Milestone payments	$ 17,500
GSK Agreement
Collaborative Arrangements and Non-collaborative Arrangement Transactions
Deferred revenue recognition period		36 months
Number of optional additional targets \| person		2
Number of development candidates \| person		1
Remaining performance obligation			$ 0
Revised, increased research period			36 months
GSK Agreement \| Up-front Payment Arrangement
Collaborative Arrangements and Non-collaborative Arrangement Transactions
Upfront payment received under collaboration agreement		$ 2,500
GSK Agreement \| License, Research, Clinical Development and Commercialization
Collaborative Arrangements and Non-collaborative Arrangement Transactions
Milestone payments			$ 20,000
GSK Agreement \| Research and Development Plans and Designation of Development Candidates
Collaborative Arrangements and Non-collaborative Arrangement Transactions
Milestone payments			1,000
GSK Agreement \| Clinical and Commercial Milestones
Collaborative Arrangements and Non-collaborative Arrangement Transactions
Milestone payments		$ 89,000	$ 17,000
GSK Agreement \| Maximum
Collaborative Arrangements and Non-collaborative Arrangement Transactions
Anticipated initial collaboration term		4 years
Maximum royalty percentage on net sales			5.00%
GSK Agreement \| Maximum \| License, Research, Clinical Development and Commercialization
Collaborative Arrangements and Non-collaborative Arrangement Transactions
Milestone payments		$ 100,000
GSK Agreement \| Maximum \| Research and Development Plans and Designation of Development Candidates
Collaborative Arrangements and Non-collaborative Arrangement Transactions
Milestone payments		$ 9,000
GSK Agreement \| Minimum
Collaborative Arrangements and Non-collaborative Arrangement Transactions
Anticipated initial collaboration term		2 years
R&D Services Unit of Accounting \| GSK Agreement \| Up-front Payment Arrangement
Collaborative Arrangements and Non-collaborative Arrangement Transactions
Upfront payment received under collaboration agreement		$ 2,500