Basic and Diluted Net Loss Per Share - Additional Information (Detail) - shares	Sep. 30, 2019	Sep. 30, 2018
Earnings Per Share [Abstract]
Stock options and RSUs outstanding (in shares)	10,370,481	8,770,775

Share based compensation arrangement by share based payment award options and restricted stock units outstanding number.

No definition available.

Name:	sgmo_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsAndRestrictedStockUnitsOutstandingNumber
Namespace Prefix:	sgmo_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	instant