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Marketable Securities - Additional Information (Detail) - USD ($) | 12 Months Ended
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Dec. 31, 2016 | Dec. 31, 2015 | Dec. 31, 2014
Investments Debt And Equity Securities [Abstract] |  |  |
Investments maturity period | 1 year |  |
Realized losses of available-for-sale securities | $ 0 | $ 0 | $ 0
Investments other-than-temporarily impaired | $ 0 | $ 0 | $ 0

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- Definition Investments maturity dates available for sale securities. + References No definition available. + Details
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Balance Type: | na
Period Type: | duration

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- Definition Other than temporarily impaired investment. + References No definition available. + Details
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Namespace Prefix: | sgmo_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

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- Definition This item represents the gross loss realized on the sale of debt or equity securities categorized neither as held-to-maturity nor trading securities. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 9 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=73527792&loc=d3e27357-111563 + Details
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- References No definition available. + Details
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