Employee Stock Benefit Plans - Restricted Stock Units (Details)	12 Months Ended
Dec. 31, 2018 shares
Restricted Stock Units
Stock Benefit Plans
Right to number of shares of common stock per RSU (in shares)	1

Right to receive this specified number of shares of common stock per restricted stock unit.

No definition available.

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Namespace Prefix:	irwd_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	duration