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Stockholders' Equity - Additional Information (Detail) (USD $) | 12 Months Ended | 0 Months Ended
--- | --- | ---
Dec. 31, 2014 | Dec. 31, 2013 | Dec. 31, 2012 | Mar. 25, 2014 | Sep. 23, 2013
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |
Preferred shares authorized | 5,000,000 us-gaap_PreferredStockSharesAuthorized |  |  |  |
Proceeds from public offering of common stock, net of issuance costs | $ 93,796,000 sgmo_NetProceedsFromIssuancePublicOffering | $ 69,492,000 sgmo_NetProceedsFromIssuancePublicOffering |  |  |
Stock option maximum term | 5 years 26 days |  |  |  |
Specified stockholder ownership percentage | 10.00%sgmo_SpecifiedStockholderOwnershipPercentage |  |  |  |
Purchase price of common stock percent under stock incentive plans for specified stockholder | 110.00%sgmo_ShareBasedCompensationArrangementByShareBasedPaymentAwardPurchasePriceOfCommonStockPercentForSpecifiedStockholder |  |  |  |
Stock option maximum term for specified stockholder | 5 years |  |  |  |
Share of common stock subject to a stock option or stock appreciation right | 1 sgmo_CommonStockExchangeRatio |  |  |  |
Fixed ratio shares of common stock | 1.33 us-gaap_StockholdersEquityNoteStockSplitConversionRatio1 |  |  |  |
Intrinsic value of options exercised | 20,400,000 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisesInPeriodTotalIntrinsicValue | 8,900,000 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisesInPeriodTotalIntrinsicValue | 600,000 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisesInPeriodTotalIntrinsicValue |  |
Options outstanding, Aggregate Intrinsic Value | 50,766,000 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingIntrinsicValue |  |  |  |
Options exercisable, Aggregate Intrinsic Value | 39,475,000 us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsExercisableIntrinsicValue1 |  |  |  |
Options vested and expected to vest, aggregate intrinsic value | 49,400,000 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedAndExpectedToVestExercisableAggregateIntrinsicValue | 54,900,000 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedAndExpectedToVestExercisableAggregateIntrinsicValue | 8,500,000 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedAndExpectedToVestExercisableAggregateIntrinsicValue |  |
Restricted stock units awarded | 488,000 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod |  |  |  |
Aggregate value of shares vested in period | 9,100,000 us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardEquityInstrumentsOtherThanOptionsAggregateIntrinsicValueVested | 4,100,000 us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardEquityInstrumentsOtherThanOptionsAggregateIntrinsicValueVested | 100,000 us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardEquityInstrumentsOtherThanOptionsAggregateIntrinsicValueVested |  |
Total payments for the employees' tax obligations to taxing authorities | 4,556,000 us-gaap_PaymentsRelatedToTaxWithholdingForShareBasedCompensation | 2,015,000 us-gaap_PaymentsRelatedToTaxWithholdingForShareBasedCompensation |  |  |
2013 Stock Incentive Plan [Member] |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |
Percent of fair value per share of common stock on option grant date | 100.00%us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardPurchasePriceOfCommonStockPercent / us-gaap_PlanNameAxis = sgmo_TwoThousandThirteenStockIncentivePlanMember |  |  |  |
Stock options vesting period | 4 years |  |  |  |
Stock options expiration term | 10 years |  |  |  |
Stock reserved for issuance under plan | 14,100,000 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAuthorized / us-gaap_PlanNameAxis = sgmo_TwoThousandThirteenStockIncentivePlanMember |  |  |  |
Additional shares authorized under 2013 stock incentive plan | 4,400,000 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfAdditionalSharesAuthorized / us-gaap_PlanNameAxis = sgmo_TwoThousandThirteenStockIncentivePlanMember |  |  |  |
Shares reserved for issuance of future awards | 768,044 us-gaap_CommonStockCapitalSharesReservedForFutureIssuance / us-gaap_PlanNameAxis = sgmo_TwoThousandThirteenStockIncentivePlanMember |  |  |  |
2004 Stock Incentive Plan [Member] |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |
Stock reserved for issuance under plan | 9,700,000 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAuthorized / us-gaap_PlanNameAxis = sgmo_TwoThousandFourStockIncentivePlanMember |  |  |  |
2010 Employee Stock Purchase Plan [Member] |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |
Percent of fair value per share of common stock on option grant date | 85.00%us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardPurchasePriceOfCommonStockPercent / us-gaap_PlanNameAxis = us-gaap_EmployeeStockMember |  |  |  |
Stock reserved for issuance under plan | 2,100,000 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAuthorized / us-gaap_PlanNameAxis = us-gaap_EmployeeStockMember |  |  |  |
Purchase plan offering period | 2 years |  |  |  |
Purchase plan purchase period | 6 months |  |  |  |
Shares reserved for issuance of future awards | 1,420,560 us-gaap_CommonStockCapitalSharesReservedForFutureIssuance / us-gaap_PlanNameAxis = us-gaap_EmployeeStockMember |  |  |  |
Maximum [Member] | 2013 Stock Incentive Plan [Member] |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |
Stock option maximum term | 10 years |  |  |  |
Stock Option Activity [Member] |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |
Shares subject to repurchase rights | 0 us-gaap_WeightedAverageNumberOfSharesCommonStockSubjectToRepurchaseOrCancellation / us-gaap_AwardTypeAxis = us-gaap_StockOptionMember |  |  |  |
Stock Option Activity [Member] | 2013 Stock Incentive Plan [Member] |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |
Share based vesting rights | Options granted under the 2013 Plan generally vest over four years at a rate of 25 percent one year from the grant date and one thirty-sixth per month thereafter and expire ten years after the grant, or earlier upon employment termination. |  |  |  |
Stock options granted vesting percentage | 25.00%sgmo_ShareBasedCompensationArrangementByShareBasedPaymentAwardVestingPercentage / us-gaap_AwardTypeAxis = us-gaap_StockOptionMember / us-gaap_PlanNameAxis = sgmo_TwoThousandThirteenStockIncentivePlanMember |  |  |  |
Restricted Stock Units (RSUs) [Member] |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |
Share based vesting rights | These awards will vest as follows: one-third of the award will vest in a series of three successive equal annual installments. |  |  |  |
Restricted stock units awarded | 488,000 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod / us-gaap_AwardTypeAxis = us-gaap_RestrictedStockUnitsRSUMember | 392,500 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod / us-gaap_AwardTypeAxis = us-gaap_RestrictedStockUnitsRSUMember |  |  |
Grant date fair value of restricted stock units awarded | $ 14.05 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue / us-gaap_AwardTypeAxis = us-gaap_RestrictedStockUnitsRSUMember | $ 12.12 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue / us-gaap_AwardTypeAxis = us-gaap_RestrictedStockUnitsRSUMember |  |  |
Share-based compensation arrangement by share-based payment award, number of vesting installment | 3 sgmo_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfVestingInstallment / us-gaap_AwardTypeAxis = us-gaap_RestrictedStockUnitsRSUMember |  |  |  |
Share-based compensation arrangement by share-based payment award, vesting portion | 0.33%sgmo_ShareBasedCompensationArrangementByShareBasedPaymentAwardVestingPortion / us-gaap_AwardTypeAxis = us-gaap_RestrictedStockUnitsRSUMember |  |  |  |
Shares withheld from issuance in order to pay employee taxes | 309,102 us-gaap_SharesPaidForTaxWithholdingForShareBasedCompensation / us-gaap_AwardTypeAxis = us-gaap_RestrictedStockUnitsRSUMember | 167,138 us-gaap_SharesPaidForTaxWithholdingForShareBasedCompensation / us-gaap_AwardTypeAxis = us-gaap_RestrictedStockUnitsRSUMember | 0 us-gaap_SharesPaidForTaxWithholdingForShareBasedCompensation / us-gaap_AwardTypeAxis = us-gaap_RestrictedStockUnitsRSUMember |  |
Common Stock [Member] |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |
Public offering, common stock shares issued | 4,444,444 us-gaap_StockIssuedDuringPeriodSharesNewIssues / us-gaap_StatementEquityComponentsAxis = us-gaap_CommonStockMember | 7,015,000 us-gaap_StockIssuedDuringPeriodSharesNewIssues / us-gaap_StatementEquityComponentsAxis = us-gaap_CommonStockMember |  | 4,444,444 us-gaap_StockIssuedDuringPeriodSharesNewIssues / us-gaap_StatementEquityComponentsAxis = us-gaap_CommonStockMember | 7,015,000 us-gaap_StockIssuedDuringPeriodSharesNewIssues / us-gaap_StatementEquityComponentsAxis = us-gaap_CommonStockMember
Public offering price of common stock issued |  |  |  | $ 22.50 us-gaap_SharesIssuedPricePerShare / us-gaap_StatementEquityComponentsAxis = us-gaap_CommonStockMember | $ 10.58 us-gaap_SharesIssuedPricePerShare / us-gaap_StatementEquityComponentsAxis = us-gaap_CommonStockMember
Proceeds from public offering of common stock, net of issuance costs |  |  |  | $ 93,800,000 sgmo_NetProceedsFromIssuancePublicOffering / us-gaap_StatementEquityComponentsAxis = us-gaap_CommonStockMember | $ 69,500,000 sgmo_NetProceedsFromIssuancePublicOffering / us-gaap_StatementEquityComponentsAxis = us-gaap_CommonStockMember
Underwriters | Common Stock [Member] |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |
Sale of stock, number of shares issued in transaction |  |  |  |  | 915,000 us-gaap_SaleOfStockNumberOfSharesIssuedInTransaction / us-gaap_RelatedPartyTransactionsByRelatedPartyAxis = sgmo_UnderwritersMember / us-gaap_StatementEquityComponentsAxis = us-gaap_CommonStockMember

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- Definition Aggregate number of common shares reserved for future issuance. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.29) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 + Details
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- Definition Amount of cash outflow to satisfy an employee's income tax withholding obligation as part of a net-share settlement of a share-based award. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 15 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3291-108585 + Details
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- Definition The maximum number of nonredeemable preferred shares (or preferred stock redeemable solely at the option of the issuer) permitted to be issued by an entity's charter and bylaws. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.28) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 29 -Article 5 + Details
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- Definition Period which an employee's right to exercise an award is no longer contingent on satisfaction of either a service condition, market condition or a performance condition, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (a)(1) -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901 + Details
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- Definition Description of award terms as to how many shares or portion of an award are no longer contingent on satisfaction of either a service condition, market condition or a performance condition, thereby giving the employee the legal right to convert the award to shares, to sell the shares, and be entitled to the cash proceeds of such sale. For example, vesting may be expressed as being 25 percent of the shares under option on each anniversary of the grant date. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (a)(1) -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901 + Details
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- Definition Intrinsic value of equity-based compensation awards vested. Excludes stock and unit options. + References No definition available. + Details
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- Definition The number of grants made during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan). + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c)(2)(iii)(1) -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901 + Details
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- Definition The weighted average fair value at grant date for nonvested equity-based awards issued during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan). + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c)(2)(iii)(1) -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901 + Details
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- Definition Number of additional shares authorized for issuance under an established share-based compensation plan. + References No definition available. + Details
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- Definition The maximum number of shares (or other type of equity) originally approved (usually by shareholders and board of directors), net of any subsequent amendments and adjustments, for awards under the equity-based compensation plan. As stock or unit options and equity instruments other than options are awarded to participants, the shares or units remain authorized and become reserved for issuance under outstanding awards (not necessarily vested). + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (a)(3) -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901 + Details
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- Definition Amount of difference between fair value of the underlying shares reserved for issuance and exercise price of vested portions of options outstanding and currently exercisable. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901 + Details
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- Definition Weighted average remaining contractual term for vested portions of options outstanding and currently exercisable or convertible, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901 + Details
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- Definition Amount of accumulated difference between fair value of underlying shares on dates of exercise and exercise price on options exercised (or share units converted) into shares. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (d)(2) -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901 + Details
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- Definition Amount by which the current fair value of the underlying stock exceeds the exercise price of options outstanding. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901 + Details
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- Definition Amount of difference between fair value of the underlying shares reserved for issuance and exercise price of fully vested and expected to vest options that are exercisable. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (e)(2) -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901 + Details
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- Definition Amount per share or per unit of equity securities issued by non-development stage entity. + References No definition available. + Details
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- Definition For net-share settlement of share-based awards when the employer settles employees' income tax withholding obligations, this element represents the number of shares the employees use to repay the employer. + References No definition available. + Details
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- Definition Ratio applied to the conversion of stock split, for example but not limited to, one share converted to two or two shares converted to one. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Stock Split -URI http://asc.fasb.org/extlink&oid=6525746 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 505 -SubTopic 10 -Section S99 -Paragraph 4 -Subparagraph (SAB TOPIC 4.C) -URI http://asc.fasb.org/extlink&oid=27012166&loc=d3e187143-122770 + Details
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