Assets accumulated gross unrealized gain before tax.

No definition available.

Name:	sgmo_AssetsAccumulatedGrossUnrealizedGainBeforeTax
Namespace Prefix:	sgmo_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Assets accumulated gross unrealized loss before tax.

+ References

No definition available.

+ Details

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

- Definition

Assets amortized cost.

+ References

No definition available.

+ Details

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

- Definition

Cash and cash equivalents accumulated gross unrealized gain before tax.

+ References

No definition available.

+ Details

Name:	sgmo_CashAndCashEquivalentsAccumulatedGrossUnrealizedGainBeforeTax
Namespace Prefix:	sgmo_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Fair value portion of probable future economic benefits obtained or controlled by an entity as a result of past transactions or events.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=66048111&loc=d3e19207-110258

+ Details

Name:	us-gaap_AssetsFairValueDisclosure
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amount of currency on hand as well as demand deposits with banks or financial institutions. Includes other kinds of accounts that have the general characteristics of demand deposits. Also includes short-term, highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates. Excludes cash and cash equivalents within disposal group and discontinued operation.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Glossary Cash
-URI http://asc.fasb.org/extlink&oid=6506951

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section 45
-Paragraph 1
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=28358313&loc=d3e6676-107765

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 4
-URI http://asc.fasb.org/extlink&oid=66902209&loc=d3e3044-108585

Reference 4: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Glossary Cash Equivalents
-URI http://asc.fasb.org/extlink&oid=6507016

Reference 5: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.1)
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

+ Details

Name:	us-gaap_CashAndCashEquivalentsAtCarryingValue
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Fair value portion of currency on hand as well as demand deposits with banks or financial institutions. Includes other kinds of accounts that have the general characteristics of demand deposits. Also includes short-term, highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates.

+ References

+ Details

Name:	us-gaap_CashAndCashEquivalentsFairValueDisclosure
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- 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_InformationByCategoryOfDebtSecurityAxis=us-gaap_AvailableforsaleSecuritiesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_InvestmentTypeAxis=us-gaap_MoneyMarketFundsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_InvestmentTypeAxis=us-gaap_CashEquivalentsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_InvestmentTypeAxis=us-gaap_CommercialPaperMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis=us-gaap_USGovernmentSponsoredEnterprisesDebtSecuritiesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis=us-gaap_CorporateDebtSecuritiesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Marketable Securities - Schedule of Investments (Detail) - USD ($) $ in Thousands	Sep. 30, 2016	Dec. 31, 2015	Sep. 30, 2015	Dec. 31, 2014
Schedule Of Available For Sale Securities [Line Items]
Cash and cash equivalents	$ 27,986	$ 69,482	$ 34,287	$ 6,030
Total cash equivalents	27,115	65,937
Amortized Cost	154,089	205,440
Gross Unrealized Gains	129	51
Gross Unrealized (Losses)	(1)	(36)
Estimated Fair Value	154,217	205,455
Available-for-sale securities [Member]
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	126,974	139,504
Gross Unrealized Gains	129	50
Gross Unrealized (Losses)	(1)	(36)
Estimated Fair Value	127,102	139,518
Money market funds [Member]
Schedule Of Available For Sale Securities [Line Items]
Cash and cash equivalents	24,113	25,070
Total cash equivalents	24,113	25,070
Cash equivalents [Member]
Schedule Of Available For Sale Securities [Line Items]
Cash and cash equivalents	27,115	65,936
Gross Unrealized Gains		1
Total cash equivalents	27,115	65,937
Commercial paper securities [Member]
Schedule Of Available For Sale Securities [Line Items]
Cash and cash equivalents		2,000
Total cash equivalents		2,000
Commercial paper securities [Member] \| Available-for-sale securities [Member]
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	25,655	30,667
Gross Unrealized Gains	74	50
Estimated Fair Value	25,729	30,717
U.S. government sponsored entity debt securities [Member]
Schedule Of Available For Sale Securities [Line Items]
Cash and cash equivalents	3,002	38,866
Gross Unrealized Gains		1
Total cash equivalents	3,002	38,867
U.S. government sponsored entity debt securities [Member] \| Available-for-sale securities [Member]
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	91,309	91,562
Gross Unrealized Gains	55
Gross Unrealized (Losses)		(24)
Estimated Fair Value	91,364	91,538
Corporate debt securities [Member] \| Available-for-sale securities [Member]
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	10,010	17,275
Gross Unrealized (Losses)	(1)	(12)
Estimated Fair Value	$ 10,009	$ 17,263