Fair Value Measurements - Additional Information (Details) - USD ($)	3 Months Ended
Mar. 31, 2018	Mar. 31, 2017
Fair Value Disclosures [Abstract]
Transfers between fair value measure levels	$ 0	$ 0

Fair value assets (liabilities) transfer between levels.

No definition available.

Name:	fixx_FairValueAssetsLiabilitiesTransferBetweenLevels
Namespace Prefix:	fixx_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration