Represents the percentage of discount on share price treated as expense recognized during the period arising from equity-based compensation arrangements (for example, shares of stock, unit, stock options or other equity instruments) with employees, directors and certain consultants qualifying for treatment as employees.

No definition available.

+ Details

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

- Definition

The aggregate amount of noncash, equity-based employee remuneration. This may include the value of stock or unit options, amortization of restricted stock or units, and adjustment for officers' compensation. As noncash, this element is an add back when calculating net cash generated by operating activities using the indirect method.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 28
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=109223946&loc=d3e3602-108585

+ Details

Name:	us-gaap_ShareBasedCompensation
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
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_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

The weighted average grant-date fair value of options granted during the reporting period as calculated by applying the disclosed option pricing methodology.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (d)(1)
-URI http://asc.fasb.org/extlink&oid=109197908&loc=d3e5070-113901

+ Details

Name:	us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageGrantDateFairValue
Namespace Prefix:	us-gaap_
Data Type:	num:perShareItemType
Balance Type:	na
Period Type:	duration

- Details

Name:	us-gaap_IncomeStatementLocationAxis=us-gaap_ResearchAndDevelopmentExpenseMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_StatementClassOfStockAxis=idra_EmployeeStockPurchasePlanMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_StatementClassOfStockAxis=idra_StockIncentivePlanMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_IncomeStatementLocationAxis=us-gaap_GeneralAndAdministrativeExpenseMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_IncomeStatementLocationAxis=us-gaap_RestructuringChargesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Stock-Based Compensation - Accounting for Stock-based Compensation (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Share-based Compensation Arrangement by Share-based Payment Award
Percentage of share-based compensation expense			15.00%
Weighted average grant date fair value of options granted during the period (per share)			$ 7.15	$ 8.08
Stock-based compensation	$ 1,327	$ 1,623	$ 4,454	$ 9,165
Research and development
Share-based Compensation Arrangement by Share-based Payment Award
Stock-based compensation	314	589	1,441	5,972
Research and development \| Employee Stock Purchase Plans
Share-based Compensation Arrangement by Share-based Payment Award
Stock-based compensation	11	26	62	68
Research and development \| Equity Incentive Plans
Share-based Compensation Arrangement by Share-based Payment Award
Stock-based compensation	303	563	1,379	5,904
General and administrative
Share-based Compensation Arrangement by Share-based Payment Award
Stock-based compensation	989	1,034	2,989	3,193
General and administrative \| Employee Stock Purchase Plans
Share-based Compensation Arrangement by Share-based Payment Award
Stock-based compensation	8	18	40	48
General and administrative \| Equity Incentive Plans
Share-based Compensation Arrangement by Share-based Payment Award
Stock-based compensation	981	$ 1,016	2,949	$ 3,145
Restructuring costs \| Employee Stock Purchase Plans
Share-based Compensation Arrangement by Share-based Payment Award
Stock-based compensation	$ 24		$ 24