Advance received under loan and security agreement.

No definition available.

Name:	idra_AdvanceReceivedUnderLoanAndSecurityAgreement
Namespace Prefix:	idra_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Debt instrument debt default percentage.

+ References

No definition available.

+ Details

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

- Definition

Number of debt instrument payments consisting of principal and accrued interest.

+ References

No definition available.

+ Details

Name:	idra_DebtInstrumentNumberOfRepaymentInstallmentsThatIncludePrincipal
Namespace Prefix:	idra_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

- Definition

Final payment of additional interest as a percentage of aggregate amount advanced.

+ References

No definition available.

+ Details

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

- Definition

Borrowing capacity under the loan and security agreement.

+ References

No definition available.

+ Details

Name:	idra_LoanAndSecurityAgreementBorrowingCapacity
Namespace Prefix:	idra_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Maximum prepayment fee rate.

+ References

No definition available.

+ Details

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

- Definition

Minimum interest rate.

+ References

No definition available.

+ Details

Name:	idra_MinimumInterestRate
Namespace Prefix:	idra_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Minimum prepayment fee rate.

+ References

No definition available.

+ Details

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

- Definition

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

+ References

No definition available.

+ Details

Name:	us-gaap_DebtInstrumentBasisSpreadOnVariableRate1
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Effective interest rate for the funds borrowed under the debt agreement considering interest compounding and original issue discount or premium.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.22(a)(1))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=64930785&loc=d3e28551-108399

+ Details

Name:	us-gaap_DebtInstrumentInterestRateEffectivePercentage
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Description of the interest rate as being fixed or variable, and, if variable, identification of the index or rate on which the interest rate is based and the number of points or percentage added to that index or rate to set the rate, and other pertinent information, such as frequency of rate resets.

+ References

+ Details

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

- Definition

Sum of the carrying values as of the balance sheet date of the portions of long-term notes payable due within one year or the operating cycle if longer.

+ References

+ Details

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

- Details

Name:	us-gaap_CounterpartyNameAxis=idra_OxfordMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_VariableRateAxis=us-gaap_LondonInterbankOfferedRateLIBORMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Note Payable (Details) $ in Thousands	12 Months Ended	15 Months Ended
Note Payable (Details) $ in Thousands	Dec. 31, 2017 USD ($) installment	Dec. 31, 2015 USD ($)	Dec. 31, 2016 USD ($)
Debt Instrument
Current portion of note payable	$ 209		$ 292
Advance received under loan and security agreement	$ 900
Oxford
Debt Instrument
Borrowing capacity under the loan and security agreement		$ 3,000
Minimum interest rate		7.50%
Number of debt instrument payments \| installment	36
Final payment of additional interest as a percentage of aggregate amount advanced	5.70%
Weighted average annual effective interest rate	11.10%
Minimum prepayment fee interest rate percentage	1.00%
Current portion of note payable	$ 200
Maximum prepayment fee interest rate percentage	3.00%
Outstanding loan balance, default interest rate	5.00%
Oxford \| Three months US LIBOR
Debt Instrument
Basis spread on fixed interest rate set at time of advance		7.27%
Description of interest rate	three-month U.S. Libor Rate