Business acquisition, number of free shares held by the holders.

No definition available.

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

- Definition

Business Acquisition, Number Of Free Shares Outstanding Subject To Purchase

+ References

No definition available.

+ Details

Name:	sgmo_BusinessAcquisitionNumberOfFreeSharesOutstandingSubjectToPurchase
Namespace Prefix:	sgmo_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	duration

- Definition

Business Acquisitions, Fair Value of Free Shares' Asset

+ References

No definition available.

+ Details

Name:	sgmo_BusinessAcquisitionsFairValueOfFreeSharesAsset
Namespace Prefix:	sgmo_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

The cash outflow associated with the purchase of noncontrolling interest during the period.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 13
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=123570139&loc=d3e3213-108585

+ Details

Name:	us-gaap_PaymentsToAcquireAdditionalInterestInSubsidiaries
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

+ Details

Name:	us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Details

Name:	us-gaap_BusinessAcquisitionAxis=sgmo_SangamoFranceMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_TypeOfArrangementAxis=sgmo_SharePurchaseAgreementAndTenderOfferAgreementMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

FAIR VALUE MEASUREMENTS - Narrative (Detail) - USD ($)	6 Months Ended
FAIR VALUE MEASUREMENTS - Narrative (Detail) - USD ($)	Jun. 30, 2021	Jun. 30, 2020	Dec. 31, 2020	Jul. 20, 2018
Debt Securities, Available-for-sale [Line Items]
Purchase of additional Sangamo France shares	$ 119,000	$ 237,000
Sangamo France \| Share purchase agreement and tender offer agreement
Debt Securities, Available-for-sale [Line Items]
Number of free shares held by the holders (in shares)				477,000
Purchase of additional Sangamo France shares	$ 1,100,000
Number of free shares outstanding subject to purchase (in shares)	0
Business Acquisitions, Fair Value of Free Shares' Asset	$ 0		$ 0