Collaboration,License and Co-Promotion Agreements - Other Collaborations and License Agreements (Details) $ in Millions	9 Months Ended
Sep. 30, 2016 USD ($)
Agreement One - other collaboration and license agreements \| Development milestones
Collaboration, License and Co-Promotion Agreements
Contingent milestone payable	$ 7.5
Milestone payment made	2.5
Agreement One - other collaboration and license agreements \| Regulatory milestones
Collaboration, License and Co-Promotion Agreements
Contingent milestone payable	18.0
Milestone payment made	0.0
Agreement Two - other collaboration and license agreements
Collaboration, License and Co-Promotion Agreements
Contingent milestone payable per product, maximum	114.5
Agreement Two - other collaboration and license agreements \| Sales milestones
Collaboration, License and Co-Promotion Agreements
Contingent milestone payable per product	35.0
Agreement Two - other collaboration and license agreements \| Development milestones
Collaboration, License and Co-Promotion Agreements
Contingent milestone payable per product	21.5
Agreement Two - other collaboration and license agreements \| Regulatory milestones
Collaboration, License and Co-Promotion Agreements
Contingent milestone payable per product	$ 58.0

Represents the amount of milestone paid under the collaboration agreements.

No definition available.

Name:	irwd_CollaborativeArrangementMilestonePaid
Namespace Prefix:	irwd_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Represents the amount of contingent milestone payments payable by the entity upon achievement of certain development and commercialization milestones.

+ References

No definition available.

+ Details

Name:	irwd_ContingentMilestonePaymentsPayable
Namespace Prefix:	irwd_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Represents the maximum amount of contingent milestone payable by the Company (per product) upon achievement of certain development and commercialization milestones.

+ References

No definition available.

+ Details

Name:	irwd_ContingentMilestonePaymentsPayableMaximumPerProduct
Namespace Prefix:	irwd_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Represents the amount of contingent milestone payable by the Company (per product) upon achievement of certain development and commercialization milestones.

+ References

No definition available.

+ Details

Name:	irwd_ContingentMilestonePaymentsPayablePerProduct
Namespace Prefix:	irwd_
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_CollaborativeArrangementsAndNoncollaborativeArrangementTransactionsLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Details

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

- Details

Name:	irwd_AchievementOfMilestoneAxis=irwd_DevelopmentMilestonesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	irwd_AchievementOfMilestoneAxis=irwd_RegulatoryMilestonesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

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

- Details

Name:	irwd_AchievementOfMilestoneAxis=irwd_SalesMilestonesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: