Represents the number of transition services agreement.

No definition available.

Name:	irwd_NumberOfTransitionServicesAgreements
Namespace Prefix:	irwd_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- Definition

Transitional Services Agreement, Initial Term of Service, High End of Range

+ References

No definition available.

+ Details

Name:	irwd_TransitionalServicesAgreementInitialTermOfServiceHighEndOfRange
Namespace Prefix:	irwd_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Transitional Services Agreement, Initial Term of Service, Low End of Range

+ References

No definition available.

+ Details

Name:	irwd_TransitionalServicesAgreementInitialTermOfServiceLowEndOfRange
Namespace Prefix:	irwd_
Data Type:	xbrli:durationItemType
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_RelatedPartyTransactionLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

The aggregate costs incurred (1) in a planned search or critical investigation aimed at discovery of new knowledge with the hope that such knowledge will be useful in developing a new product or service, a new process or technique, or in bringing about a significant improvement to an existing product or process; or (2) to translate research findings or other knowledge into a plan or design for a new product or process or for a significant improvement to an existing product or process whether intended for sale or the entity's use, during the reporting period charged to research and development projects, including the costs of developing computer software up to the point in time of achieving technological feasibility, and costs allocated in accounting for a business combination to in-process projects deemed to have no alternative future use.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 985
-SubTopic 20
-Section 50
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=6501960&loc=d3e128462-111756

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 730
-SubTopic 10
-Section 50
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=6420194&loc=d3e21568-108373

+ Details

Name:	us-gaap_ResearchAndDevelopmentExpense
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Carrying amount as of the balance sheet date of improvements having a life longer than one year that were made for the benefit of one or more tenants.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03.1(f))
-URI http://asc.fasb.org/extlink&oid=119400593&loc=d3e572229-122910

+ Details

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

- Details

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

- Details

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

- Details

Name:	us-gaap_DisposalGroupClassificationAxis=irwd_DevelopmentAgreementMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Cyclerion Separation - General Information (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2020 USD ($) agreement	Mar. 31, 2019 USD ($)	Dec. 31, 2019 USD ($)
Cyclerion Separation
Transition services agreements \| agreement	2
Initial term of service, low end of range	1 year
Initial term of service, high end of range	2 years
Research and Development Expense	$ 28,027	$ 32,198
Affiliated Entity
Cyclerion Separation
Tenant improvement reimbursement provisions			$ 1,300
Affiliated Entity \| Research and development \| Development Agreement [Member]
Cyclerion Separation
Research and Development Expense	$ 1,000