Commitments and Contingencies (Details) $ in Thousands	6 Months Ended
Jun. 30, 2026 USD ($)
Commitments and Contingencies Disclosure [Abstract]
Potential payments upon achievement of milestones	$ 18,000
Duration of time milestone payments are not expected to be paid to third parties	12 months

Duration of time milestone payments are not expected to be paid to third parties, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. Includes, but not limited to, weeks in a year or quarter.

No definition available.

Name:	rytm_DurationMilestonePaymentsNotExpectingToBePaid
Namespace Prefix:	rytm_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration