Inventory (Details) $ in Millions	9 Months Ended
Sep. 30, 2016 USD ($) agreement	Dec. 31, 2015 USD ($)
Inventory
Number of minimum supply agreements (in agreements) \| agreement	2
Accrual for excess purchase commitments \| $	$ 10.1	$ 10.1

Carrying value as of the balance sheet date of the reduction in the value of purchase commitments.

No definition available.

Name:	irwd_AccruedLossPurchaseCommitments
Namespace Prefix:	irwd_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant