Sangamo Therapeutics (SGMO) 10-K 28 Feb 20 2019 FY Annual report Financial data

Cover

Cover - USD ($)	12 Months Ended
	Dec. 31, 2019	Feb. 21, 2020	Jun. 30, 2019
Cover page.
Document Type	10-K
Document Annual Report	true
Document Period End Date	Dec. 31, 2019
Document Transition Report	false
Entity File Number	000-30171
Entity Registrant Name	SANGAMO THERAPEUTICS, INC.
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	68-0359556
Entity Address, Address Line One	7000 Marina Blvd.
Entity Address, City or Town	Brisbane
Entity Address, State or Province	CA
Entity Address, Postal Zip Code	94005
City Area Code	510
Local Phone Number	970-6000
Title of 12(b) Security	Common Stock, par value $0.01 per share
Trading Symbol	SGMO
Security Exchange Name	NASDAQ
Entity Well-known Seasoned Issuer	Yes
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Public Float			$ 1,244,723,752
Entity Common Stock, Shares Outstanding		116,022,630
Documents Incorporated by Reference	Certain information required by Part III, Items 10-14 of this Form 10-K is incorporated by reference to the registrant’s definitive Proxy Statement for the 2020 Annual Meeting of Stockholders to be filed with the Securities and Exchange Commission pursuant to Regulation 14A not later than 120 days after the end of the fiscal year covered by this Form 10-K, provided that if such Proxy Statement is not filed within such period, such information will be included in an amendment to this Form 10-K to be filed within such 120-day period .
Amendment Flag	false
Document Fiscal Year Focus	2019
Document Fiscal Period Focus	FY
Entity Central Index Key	0001001233
Current Fiscal Year End Date	--12-31

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Current assets:
Cash and cash equivalents	$ 80,428	$ 140,418
Marketable securities	282,046	259,715
Interest receivable	682	375
Accounts receivable	36,909	4,673
Prepaid expenses and other current assets	5,408	5,340
Total current assets	405,473	410,521
Marketable securities, non-current	21,832	0
Property and equipment, net	29,926	78,723
Intangible assets	53,156	54,243
Goodwill	39,273	40,044
Operating lease right-of-use assets	77,289	0
Other non-current assets	9,067	3,364
Non-current restricted cash	1,500	3,500
Total assets	637,516	590,395
Current liabilities:
Accounts Payable and Accrued Liabilities, Current	17,556	21,457
Accrued compensation and employee benefits	13,605	9,490
Deferred revenues	38,711	47,564
Total current liabilities	69,872	78,511
Deferred revenues, non-current	81,432	108,273
Long-term portion of lease liabilities	41,192	0
Long-term portion of lease liabilities		27,689
Deferred income tax	6,570	6,705
Other non-current liabilities	5,711	1,960
Total liabilities	204,777	223,138
Commitments and contingencies
Stockholders' equity:
Preferred stock, $0.01 par value, 5,000,000 shares authorized and no shares issued or outstanding	0	0
Common stock, $0.01 par value; 160,000,000 shares authorized, 115,972,708 and 102,187,471 shares issued and outstanding at December 31, 2019 and 2018, respectively	1,160	1,022
Additional paid-in capital	1,090,828	929,632
Accumulated deficit	(656,985)	(562,696)
Accumulated other comprehensive loss	(2,449)	(1,440)
Total Sangamo Therapeutics, Inc. stockholders' equity	432,554	366,518
Non-controlling interest	185	739
Total stockholders' equity	432,739	367,257
Total liabilities and stockholders' equity	$ 637,516	$ 590,395

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) - $ / shares	Dec. 31, 2019	Dec. 31, 2018
Statement of Financial Position [Abstract]
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common stock, shares authorized (in shares)	160,000,000	160,000,000
Common stock, shares issued (in shares)	115,972,708	102,187,471
Common stock, shares outstanding (in shares)	115,972,708	102,187,471
Preferred stock par value (in dollars per share)	$ 0.01	$ 0.01
Preferred shares authorized (in shares)	5,000,000	5,000,000
Preferred stock issued (in shares)	0	0
Preferred stock outstanding (in shares)	0	0

Consolidated Statements of Oper

Consolidated Statements of Operations - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Revenues:
Revenues	$ 102,428	$ 84,452	$ 36,567
Operating expenses:
Research and development	145,922	114,866	65,728
General and administrative	61,686	46,736	27,200
Total operating expenses	207,608	161,602	92,928
Loss from operations	(105,180)	(77,150)	(56,361)
Interest and other income, net	9,761	8,261	1,793
Loss before income taxes	(95,419)	(68,889)	(54,568)
Benefit from income taxes	0	0	0
Net loss	(95,419)	(68,889)	(54,568)
Net loss attributable to non-controlling interest	(233)	(555)	0
Net loss attributable to Sangamo Therapeutics, Inc. stockholders	$ (95,186)	$ (68,334)	$ (54,568)
Basic and diluted net (loss) income per share attributable to Sangamo Therapeutics, Inc. (in dollars per share)	$ (0.85)	$ (0.70)	$ (0.70)
Shares used in computing basic and diluted net loss per share attributable to Sangamo Therapeutics, Inc. stockholders (in shares)	112,114	96,941	78,084

Consolidated Statements of Comp

Consolidated Statements of Comprehensive Loss - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Statement of Comprehensive Income [Abstract]
Net loss	$ (95,419)	$ (68,889)	$ (54,568)
Foreign currency translation adjustment	(1,573)	(1,148)	0
Net pension losses	(28)	(21)	0
Change in unrealized gain (loss) on available-for-sale securities	592	(4)	(306)
Comprehensive loss	(96,428)	(70,062)	(54,874)
Comprehensive loss attributable to non-controlling interest	(233)	(574)	0
Comprehensive loss attributable to Sangamo Therapeutics, Inc.	$ (96,195)	$ (69,488)	$ (54,874)

Consolidated Statements of Stoc

Consolidated Statements of Stockholders' Equity - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-in Capital	Accumulated Deficit	Accumulated Other Comprehensive Income/ (Loss)	Non- Controlling Interest
Beginning Balances (in shares) at Dec. 31, 2016		70,871,902
Beginning Balances at Dec. 31, 2016	$ 136,195	$ 709	$ 576,377	$ (440,911)	$ 20	$ 0
Issuance of common stock upon exercise of stock options and in connection with restricted stock units, net of tax (in shares)		2,101,489
Issuance of common stock upon exercise of stock options and in connection with restricted stock units, net of tax	$ 15,099	$ 21	15,078
Issuance of common stock under employee stock purchase plan (in shares)	253,994	253,994
Issuance of common stock under employee stock purchase plan	$ 818	$ 2	816
Issuance of common stock under public offering, net of issuance costs (in shares)		12,371,149
Issuance of common stock under public offering, net of issuance costs	81,573	$ 124	81,449
Stock-based compensation	9,089		9,089
Net pension losses	0
Net unrealized loss on marketable securities, net of tax	(306)				(306)
Net loss	(54,568)			(54,568)
Ending Balances (in shares) at Dec. 31, 2017		85,598,534
Ending Balances at Dec. 31, 2017	187,900	$ 856	682,809	(495,479)	(286)	0
Issuance of common stock upon exercise of stock options and in connection with restricted stock units, net of tax (in shares)		2,103,727
Issuance of common stock upon exercise of stock options and in connection with restricted stock units, net of tax	$ 14,467	$ 20	14,447
Issuance of common stock under employee stock purchase plan (in shares)	328,710	328,710
Issuance of common stock under employee stock purchase plan	$ 1,484	$ 4	1,480
Issuance of common stock under public offering, net of issuance costs (in shares)		14,156,500
Issuance of common stock under public offering, net of issuance costs	215,758	$ 142	215,616
Stock-based compensation	14,677		14,677
Acquisition of additional shares of Sangamo France	603		603
Non-controlling interest upon Acquisition of Sangamo France	1,313					1,313
Foreign currency translation adjustment	(1,148)				(1,129)	(19)
Net pension losses	(21)				(21)
Net unrealized loss on marketable securities, net of tax	(4)				(4)
Net loss	$ (68,889)			(68,334)		(555)
Ending Balances (in shares) at Dec. 31, 2018	102,187,471	102,187,471
Ending Balances at Dec. 31, 2018	$ 367,257	$ 1,022	929,632	(562,696)	(1,440)	739
Issuance of common stock upon exercise of stock options and in connection with restricted stock units, net of tax (in shares)		885,873
Issuance of common stock upon exercise of stock options and in connection with restricted stock units, net of tax	$ 3,677	$ 9	3,668
Issuance of common stock under employee stock purchase plan (in shares)	249,364	249,364
Issuance of common stock under employee stock purchase plan	$ 2,044	$ 2	2,042
Issuance of common stock under public offering, net of issuance costs (in shares)		12,650,000
Issuance of common stock under public offering, net of issuance costs	136,308	$ 127	136,181
Stock-based compensation	19,330		19,330
Acquisition of additional shares of Sangamo France	(321)					(321)
Issuance costs related to Sangamo France Acquisition	25		25
Foreign currency translation adjustment	(1,573)				(1,573)
Net pension losses	(28)				(28)
Net unrealized loss on marketable securities, net of tax	592				592
Net loss	$ (95,419)			(95,186)		(233)
Ending Balances (in shares) at Dec. 31, 2019	115,972,708	115,972,708
Ending Balances at Dec. 31, 2019	$ 432,739	$ 1,160	$ 1,090,828	$ (656,985)	$ (2,449)	$ 185

Consolidated Statements of Cash

Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Operating Activities:
Net loss	$ (95,419)	$ (68,889)	$ (54,568)
Adjustments to reconcile net loss to net cash (used in) provided by operating activities:
Depreciation and amortization	3,930	2,359	1,498
Amortization of discount on marketable securities	(4,708)	(5,829)	(673)
Amortization and other changes in right-of-use assets	(5,677)
Gain on free shares	(488)	0	0
Net loss on disposal of property and equipment	68	0	12
Stock-based compensation	19,330	14,677	9,089
Net loss on lease termination	218	0	0
Build-to-suit leases		966	80
Net changes in operating assets and liabilities:
Interest receivable	(307)	(135)	(16)
Accounts receivable	(32,236)	(1,330)	1,629
Prepaid expenses and other assets	(6,660)	(2,828)	(669)
Accounts payable and accrued liabilities	(4,192)	(6,372)	3,219
Accrued compensation and employee benefits	4,129	2,604	2,594
Deferred revenues	(35,693)	99,364	48,984
Long-term portion of lease liabilities	(1,800)
Other non-current liabilities	3,749	1,963	0
Net cash (used in) provided by operating activities	(144,402)	36,550	11,179
Investing Activities:
Acquisition, net of cash acquired	0	(75,647)	0
Purchases of marketable securities	(443,711)	(451,239)	(252,328)
Maturities of marketable securities	404,847	391,845	178,675
Purchases of property and equipment	(20,675)	(43,065)	(3,751)
Purchase of additional Sangamo France shares	(262)	0	0
Net cash used in investing activities	(59,801)	(178,106)	(77,404)
Financing Activities:
Proceeds from public offering of common stock, net of issuance costs	136,308	215,758	81,573
Taxes paid related to net share settlement of equity awards	(422)	(254)	(654)
Proceeds from issuance of common stock under employee stock purchase plan	2,044	1,484	818
Proceeds from exercise of stock options and restricted stock units	4,099	14,721	15,753
Net cash provided by financing activities	142,029	231,709	97,490
Effects of exchange rate changes on cash and cash equivalents	184	439	0
Net (decrease) increase in cash, cash equivalents, and restricted cash	(61,990)	90,592	31,265
Cash, cash equivalents, and restricted cash, beginning of period	143,918	53,326	22,061
Cash, cash equivalents, and restricted cash, end of period	81,928	143,918	53,326
Supplemental disclosure of non-cash investing activities:
Non-controlling interest for acquisition	0	1,313	0
Right-of-use assets obtained in exchange for lease obligations	31,291	0	0
Property and Equipment
Supplemental disclosure of non-cash investing activities:
Capital expenditures included in unpaid liabilities	2,114	4,953	1,214
Build-to-Suit Leases
Supplemental disclosure of non-cash investing activities:
Capital expenditures included in unpaid liabilities	$ 0	$ 2,950	$ 20,793

Organization and Summary of Sig

Organization and Summary of Significant Accounting Policies	12 Months Ended
	Dec. 31, 2019
Accounting Policies [Abstract]
Organization and Summary of Significant Accounting Policies	NOTE 1 – ORGANIZATION AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES Business Overview Sangamo Therapeutics, Inc. (“Sangamo” or “the Company”) was incorporated in the State of Delaware in June 1995 and changed its name from Sangamo Biosciences, Inc. in January 2017. Sangamo is a clinical-stage biotechnology company focused on translating ground-breaking science into genomic medicines with the potential to transform patients’ lives using our platform technologies in gene therapy, ex vivo gene-edited cell therapy, in vivo genome editing and in vivo genome regulation. Basis of Presentation The accompanying Consolidated Financial Statements have been prepared in conformity with generally accepted accounting principles in the United States of America (“U.S. GAAP”) and include the accounts of the Company and its subsidiaries. All intercompany balances and transactions have been eliminated in the Consolidated Financial Statements. For consolidated entities where we own or are exposed to less than 100% of the economics, we record net loss attributable to  non-controlling interests on our Consolidated Statements of Operations equal to the percentage of the economic or ownership interest retained in such entities by the respective noncontrolling parties. Going Concern Sangamo is currently working on a number of long-term development projects that will involve experimental technology. The projects may require several years and substantial expenditures to complete and ultimately may be unsuccessful. The Company plans to finance operations with available cash resources, collaborations and strategic partnerships funds, research grants and from the issuance of equity or debt securities. Sangamo believes that its available cash, cash equivalents and investments as of December 31, 2019, and expected revenues from collaborations, strategic partnerships and research grants, will be adequate to fund its operations at least through the next 12 months from the date the financial statements are issued. Sangamo will require substantial additional financial resources to complete the development and commercialization of its products including ZFP therapeutic products. Additional capital may not be available on terms acceptable to the Company, or at all. If adequate funds are not available, or if the terms of potential funding sources are unfavorable, the Company’s business and ability to develop its technology and therapeutic products would be harmed. Furthermore, any sales of additional equity securities may result in dilution to the Company’s stockholders, and any debt financing may include covenants that restrict the Company’s business. Reclassifications Certain prior period amounts in the accompanying Consolidated Financial Statements have been reclassified to conform to the current period presentation. Summary of Significant Accounting Policies Use of Estimates The preparation of the accompanying Consolidated Financial Statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect the amounts reported in the financial statements and the accompanying notes. On an ongoing basis, management evaluates its estimates including critical accounting policies or estimates related to revenue recognition, clinical trial accruals, fair value of assets and liabilities, including from acquisitions, and stock-based compensation. Estimates are based on historical experience and on various other market specific and other relevant assumptions that the Company believes to be reasonable under the circumstances, the results of which form the basis for making judgments about the carrying values of assets and liabilities that are not readily apparent from other sources. Actual results could differ from those estimates. In March 2019, the Company recorded an adjustment to revenue related to a change in estimate in connection with the hemophilia A collaboration agreement with Pfizer Inc. (“Pfizer”). This adjustment was a direct result of the decision to increase the project scope during the first quarter of 2019 and the corresponding costs, both of which resulted in a decrease in the measure of proportional performance. In December 2019, the Company updated its estimated project cost and related revenues upon the transfer of the investigational new drug (“IND”) for Pfizer SB-525. This adjustment directly resulted in a decrease in project scope during the fourth quarter of 2019 and a decrease in the corresponding costs, which resulted in an increase in the measure of proportional performance. These adjustments increased revenue by $5.7 million, decreased net loss by $5.7 million and decreased the Company’s basic net loss per share by $0.05 for the year ended December 31, 2019. Revenue Recognition Effective January 1, 2018, the Company adopted the provisions of Accounting Standards Codification (“ASC”) Topic 606, Revenue from Contracts with Customers (“ASC Topic 606”) using the modified retrospective method, resulting in a change to its accounting policy for revenue recognition. ASC Topic 606 establishes a unified model to determine how revenue is recognized. The Company’s contract revenues are derived from collaboration agreements and research activity grants and licensing. Research and licensing agreements typically include upfront signing or license fees, cost reimbursements, research services, minimum sublicense fees, milestone payments and royalties on future licensee’s product sales. The Company has both fixed and variable consideration. Non-refundable upfront fees and funding of research and development activities are considered fixed, while milestone payments are generally identified as variable consideration. Sangamo’s research grants are typically multi-year agreements and provide for the reimbursement of qualified expenses for research and development as defined under the terms of the grant agreement. Revenues under research grant agreements are generally recognized when the related qualified research expenses are incurred. Deferred revenue represents the portion of research or license payments received but not earned. In determining the appropriate amount of revenue to be recognized as it fulfills its obligations under its agreements, the Company performs the following steps: (i) identification of the promised goods or services in the contract; (ii) determination of whether the promised goods or services are performance obligations, including whether they are distinct in the context of the contract; (iii) measurement of the transaction price, including the constraint on variable consideration; (iv) allocation of the transaction price to the performance obligations based on estimated selling prices; and (v) recognition of revenue when (or as) the Company satisfies each performance obligation. A performance obligation is a promise in a contract to transfer a distinct good or service to the customer and is the unit of account in ASC Topic 606. The Company’s performance obligations include license rights, development services and services associated with regulatory submission and approval processes. Revenues from research services earned under collaboration agreements are generally recognized as revenue as the related services are provided. Revenues from non-refundable upfront fees are recognized over time either by measuring progress towards satisfaction of the relevant performance obligation, using the input method (i.e. cumulative actual costs incurred relative to total estimated costs) or on a straight-line basis when a performance obligation is expected to be satisfied evenly over a period of time (or when the entity has a stand-ready obligation). Significant management judgment is required to determine the level of effort required under an arrangement, and the period over which the Company expects to complete its performance obligations under the arrangement which may include total internal personnel costs and external costs to be incurred as well as, in certain cases, the estimated stand-ready obligation period. Changes in these estimates can have a material effect on revenue recognized. If the Company cannot reasonably estimate when its performance obligations either are completed or become inconsequential, then revenue recognition is deferred until the Company can reasonably make such estimates. The Company includes the unconstrained amount of estimated variable consideration in the transaction price. The amount included in the transaction price is constrained to the amount for which it is probable that a significant reversal of cumulative revenue recognized will not occur. At the end of each subsequent reporting period, the Company re-evaluates the estimated variable consideration included in the transaction price and any related constraint and, if necessary, adjusts its estimate of the overall transaction price. Revenue is then recognized over the remaining estimated period of performance using the cumulative catch-up method. The estimated period of performance and project costs, such as personnel and manufacturing cost, are reviewed quarterly and adjusted, as needed, to reflect the Company’s current assumptions regarding the timing of its deliverables. As part of the accounting for these arrangements, the Company must develop assumptions that require judgment to determine the stand-alone selling price of each performance obligation identified in the contract. The Company uses key assumptions to determine the stand-alone selling price, which may include forecasted revenues, development timelines, reimbursement rates for personnel costs, discount rates and probabilities of technical and regulatory success. Related costs and expenses under these arrangements have historically approximated the revenues recognized. Revenues from collaboration agreements and research activity grants as a percentage of total revenues were as follows: Year Ended December 31, 2019 2018 2017 Pfizer Inc. 40 % 47 % 47 % Kite Pharma, Inc. 34 % 30 % — Sanofi Genzyme 22 % 16 % 34 % Receivables from collaborations are typically unsecured and are concentrated in the biopharmaceutical industry. Accordingly, the Company may be exposed to credit risk generally associated with biopharmaceutical companies or specific to its collaboration agreements. To date, the Company has not experienced any losses related to these receivables. Funds received from third parties under contract or funds received from grant arrangements are generally recorded as revenue if the Company is deemed to be the principal participant in the arrangements because the activities under the contracts or grants are part of the Company’s development programs. Contract funds received are not refundable and are recognized when the related qualified research and development costs are incurred and there is reasonable assurance that the funds will be received. Funds received in advance are recorded as deferred revenue. Business Combinations The Company accounts for acquisitions using the acquisition method of accounting, which requires that assets acquired, including in-process research and development (“IPR&D”) projects, liabilities assumed and any non-controlling interests in the acquired target in an acquisition be recorded at their fair values as of the acquisition date on the Company’s Consolidated Balance Sheets. Any excess of purchase price over the fair value of net assets acquired is recorded as goodwill. The determination of estimated fair value requires the Company to make significant estimates and assumptions. As a result, the Company may record adjustments to the fair values of assets acquired and liabilities assumed within the measurement period (up to one year from the acquisition date) with the corresponding offset to goodwill. Transaction costs associated with business combinations are expensed as they are incurred. Goodwill and Intangible Assets Goodwill represents the excess of the consideration transferred over the estimated fair values of assets acquired and liabilities assumed in a business combination. Intangible assets with indefinite useful lives are related to purchased IPR&D projects and are measured at their respective fair values as of the acquisition date. Goodwill and intangible assets with indefinite useful lives are not amortized. Intangible assets related to IPR&D projects are considered to be indefinite-lived until the completion or abandonment of the associated research and development efforts. If and when development is complete, which generally occurs if and when regulatory approval to market a product is obtained, the associated assets would be deemed finite-lived and would then be amortized based on their respective estimated useful lives at that point in time. The Company tests goodwill and indefinite-lived intangible assets for impairment on an annual basis and between annual tests if the Company becomes aware of any events occurring or changes in circumstances that would indicate the fair values of the assets are below their respective carrying amounts. As of December 31, 2019, no impairment of goodwill or indefinite-lived intangible assets has been identified. Valuation of Long-Lived Assets Long-lived assets, including property and equipment and finite-lived intangible assets, are reviewed for impairment whenever facts or circumstances either internally or externally may suggest that the carrying value of an asset may not be recoverable. Recoverability of these assets is measured by comparison of the carrying amount of each asset to the future undiscounted cash flows expected to result from the use of the asset and its eventual disposition. If the asset is considered to be impaired, the amount of any impairment is measured as the difference between the carrying value and the fair value of the impaired asset. As of December 31, 2019, no impairment of any long-lived assets has been identified. Fair Value Measurements The carrying amounts for financial instruments consisting of cash and cash equivalents, accounts receivable, accounts payable and accrued liabilities approximate fair value due to their short maturities. Marketable securities are stated at their estimated fair values. The free share asset/liability is measured using a binomial-lattice pricing model and is reviewed each reporting period and adjusted, as needed, and is expected to approximate fair value. Cash, Cash Equivalents and Restricted Cash Sangamo considers all highly-liquid investments purchased with original maturities of three months or less at the purchase date to be cash equivalents. Cash and cash equivalents consist of cash, deposits in demand money market accounts, and commercial paper. Restricted cash consists of a letter of credit for $1.5 million as a deposit for the Brisbane lease. A reconciliation of cash, cash equivalents and restricted cash reported within the Consolidated Balance Sheets to the amounts reported within the accompanying Consolidated Statements of Cash Flows is as follows (in thousands): As of December 31, 2019 2018 2017 Cash and cash equivalents $ 80,428 $ 140,418 $ 49,826 Non-current restricted cash 1,500 3,500 3,500 Cash, cash equivalents and restricted cash as reported within the Consolidated Statements of Cash Flows $ 81,928 $ 143,918 $ 53,326 Marketable Securities Sangamo classifies its marketable securities as available-for-sale and records its investments at estimated fair value based on quoted market prices or observable market inputs of almost identical assets, with the unrealized holding gains and losses included in accumulated other comprehensive loss (“AOCI”). The Company classifies those investments that are not required for use in current operations and that mature in more than 12 months as non-current marketable securities in the accompanying Consolidated Balance Sheets. The Company’s investments are subject to a periodic impairment review. The Company recognizes an impairment charge, if material, when a decline in the fair value of its investments below the cost basis is judged to be other-than-temporary. The Company considers various factors in determining whether to recognize an impairment charge, including the length of time and extent to which the fair value has been less than the Company’s cost basis, the financial condition and near-term prospects of the investee and the Company’s intent and ability to hold the investment for a period of time sufficient to allow for any anticipated recovery in the market value. Realized gains and losses on available-for-sale securities are included in other income, net, which are determined using the specific identification method. Property and Equipment Property and equipment are stated at cost, less accumulated depreciation and amortization. Depreciation is calculated using the straight-line method based on the estimated useful lives of the related assets which is generally three Research and Development Expenses Research and development expenses consist primarily of personnel costs, including salaries, benefits and stock-based compensation, clinical studies performed by contract research organizations ("CROs"), materials and supplies and overhead allocations consisting of various support and facility-related costs. Research and development costs are expensed as incurred. General and Administrative Expenses General and administrative expenses consist of finance, human resources, legal and other administrative activities. These expenses consist primarily of personnel costs, including salaries, benefits and stock-based compensation, facilities and overhead costs, legal expenses, and other general and administrative costs. Stock-based Compensation The Company measures and recognizes compensation expense for all stock-based payment awards made to Sangamo employees and directors, including employee share options, restricted stock units (“RSUs”) and employee stock purchases related to the 2010 Employee Stock Purchase Plan (“ESPP”), as amended, based on estimated fair values at the award grant date. The fair value of stock-based awards is amortized over the vesting period of the award using a straight-line method. To estimate the fair value of an award, the Company uses the Black-Scholes option pricing model. This model requires inputs such as expected life, expected volatility and risk-free interest rate. These inputs are subjective and generally require significant analysis and judgment to develop. While estimates of expected life and volatility are derived primarily from the Company’s historical data, the risk-free rate is based on the U.S. Treasury yield curve in effect at the time of grant commensurate with the expected life assumption. The Company accounts for forfeitures in the period they occur. Income Taxes Income tax expense has been provided using the liability method. Deferred tax assets and liabilities are determined based on the difference between the financial statement and tax bases of assets and liabilities as measured by the enacted tax rates that will be in effect when these differences reverse. The Company provides a valuation allowance against net deferred tax assets if, based upon the available evidence, it is not more likely than not that the deferred tax assets will be realized. The Company recognizes a tax benefit from an uncertain tax position only if it is more likely than not that the tax position will be sustained on examination by the taxing authorities, based on the technical merits of the position. The tax benefits recognized in the Company’s consolidated financial statements from such positions are measured based on the largest benefit that has a greater than 50% likelihood of being realized. The Company recognizes interest and penalties associated with tax matters as part of the income tax provision and includes accrued interest and penalties with the related income tax liability within account payable and accrued liabilities on its Consolidated Balance Sheets. Foreign Currency Translation The functional currency of the Company’s foreign subsidiaries is primarily the Euro. Assets and liabilities denominated in foreign currencies are translated to U.S. dollars using the exchange rates at the balance sheet date. Foreign currency translation adjustments are recorded as a component of AOCI within stockholders’ equity. Revenues and expenses from the Company’s foreign subsidiaries are translated using the monthly average exchange rates in effect during the period in which the transactions occur. Foreign currency transaction gains and losses are recorded in interest and other income, net, on the Company’s Consolidated Statements of Operations. Net Loss Per Share Basic net loss per share attributable to Sangamo Therapeutics, Inc. stockholders has been computed by dividing net loss attributable to Sangamo Therapeutics, Inc. stockholders by the weighted-average number of shares of common stock outstanding during the period. Diluted net loss per share attributable to Sangamo Therapeutics, Inc. stockholders is calculated by dividing net loss attributable to Sangamo Therapeutics, Inc. stockholders by the weighted-average number of shares of common stock plus potential dilutive securities outstanding during the period. The total number of shares subject to stock options and RSUs outstanding and the ESPP shares reserved for issuance, which are all anti-dilutive, were excluded from consideration in the calculation of diluted net loss per share attributable to Sangamo Therapeutics, Inc. stockholders. Stock options and RSUs outstanding and ESPP shares reserved for issuance as of December 31, 2019, 2018 and 2017 were 10,750,550, 9,048,793, and 8,367,628, respectively. Segments The Company operates in one segment. Management uses one measure of profitability and does not segregate its business for internal reporting. As of December 31, 2019 and 2018, substantially all of the Company’s assets were maintained in the United States. For the years ended December 31, 2019, 2018 and 2017, substantially all of the Company’s revenues and operating expenses were generated and incurred in the United States. Recent Accounting Pronouncements Recently Adopted Simplified Disclosure In August 2018, the Securities and Exchange Commission ("SEC") adopted amendments to certain disclosure requirements in Securities Act Release No. 33-10532, Disclosure Update and Simplification , as updated. These amendments eliminate, modify, or integrate into other SEC requirements certain disclosure rules. Among the amendments is the requirement to present an analysis of changes in stockholders’ equity in the interim financial statements included in quarterly reports on Form 10-Q. The analysis, which can be presented as a footnote or separate statement, is required for the current and comparative quarter and year-to-date interim periods. The amendments are effective for all filings made on or after November 5, 2018. The Company’s adoption of these SEC amendments had no material effect on the Company’s reporting of financial position, results of operations, cash flows or stockholders’ equity. Accounting for Leases In February 2016, the Financial Accounting Standards Board (“FASB”) issued ASU 2016-2, Leases (“ASC Topic 842”). ASC Topic 842 amends a number of aspects of lease accounting, including requiring lessees to recognize almost all leases with a term greater than one year as a right-of-use (“ROU”) asset and corresponding liability, measured at the present value of the lease payments. On January 1, 2019, the Company adopted ASC Topic 842 using the modified retrospective approach with a cumulative-effect adjustment of $0.9 million reflected as a decrease to the opening balance of accumulated deficit as of the adoption date. Results for the year ended December 31, 2019 are presented under ASC Topic 842. No prior period amounts were adjusted and continue to be reported in accordance with previous lease guidance, ASC Topic 840 – Leases (“ASC Topic 840”). ASC Topic 842 provides a number of optional practical expedients in transition. The Company elected the practical expedients to not reassess its prior conclusions about lease identification under the new standard, to not reassess lease classification, and to not reassess initial direct costs. The Company did not elect the practical expedient allowing the use-of-hindsight, which would require the Company to reassess the lease term of its leases based on all facts and circumstances through the effective date. The Company also did not elect the practical expedient pertaining to land easements, as this is not applicable to the current contract portfolio. The impact of the adoption of ASC Topic 842 on the accompanying Consolidated Balance Sheet as of January 1, 2019 was as follows (in thousands): December 31, 2018 Adjustments Due to the Adoption of ASC Topic 842 January 1, 2019 Assets: Property and equipment, net $ 78,723 $ (62,500) $ 16,223 Operating lease right-of-use assets — 8,753 8,753 Prepaid rent — 36,025 36,025 Liabilities: Operating lease liabilities - current (1) — 1,408 1,408 Deferred rent (1) 271 (271) — Build-to-suit lease obligation (2) 27,689 (27,689) — Operating lease liabilities - long-term (2) — 7,933 7,933 Accumulated deficit (562,696) 897 (561,799) ___________________ (1) Operating lease liabilities – current and deferred rent are included in accounts payable and accrued liabilities on the Consolidated Balance Sheets. (2) Build-to-suit lease obligation and operating lease liabilities – long-term are included in long-term portion of lease liabilities on the Consolidated Balance Sheets. The adjustments due to the adoption of ASC Topic 842 primarily related to the recognition of operating lease ROU assets and operating lease liabilities for the Company’s leases. In addition, the adoption of ASC Topic 842 resulted in a change in accounting of the build-to-suit component of two leases under ASC Topic 840 to operating leases under ASC Topic 842. As a result, the Company derecognized the estimated fair value of the building shells that were included in Property and equipment, net as of December 31, 2018, as the Company had been deemed to own these buildings under ASC Topic 840. For a description of the leases, see “Note 7 – Commitments and Contingencies – Leases ” in these Consolidated Financial Statements. Not Yet Adopted Collaborative Arrangements In November 2018, the FASB issued ASU 2018-18, Collaborative Arrangements (ASC Topic 808): Clarifying the Interaction between Topic 808 and Topic 606 (“ASC Topic 808”), which clarifies that certain transactions between participants in a collaborative arrangement should be accounted for under ASC Topic 606 when the counterparty is a customer. In addition, ASC Topic 808 precludes an entity from presenting consideration from a transaction in a collaborative arrangement as revenue from contracts with customers if the counterparty is not a customer for that transaction. This guidance will be effective for the Company beginning January 1, 2020. The Company has determined the adoption of ASU 2018-18 will not have a material impact on its Consolidated Financial Statements. Goodwill Impairment Testing In January 2017, the FASB issued ASU No. 2017-4, Intangibles – Goodwill and Other (Topic 350): Simplifying the Test of Goodwill Impairment (“ASU 2017-4”). The new guidance simplifies the subsequent measurement of goodwill by eliminating Step 2 from the goodwill impairment test. ASU 2017-4 requires goodwill impairment to be measured as the amount by which a reporting unit’s carrying amount exceeds its fair value, not to exceed the carrying amount of its goodwill. ASU 2017-4 requires prospective application and is effective for annual periods beginning after December 15, 2019. ASU 2017-4 will require the Company to amend its methodology for determining any goodwill impairment beginning in 2020. The Company does not expect the adoption of ASU 2017-4 to have a material impact on its Consolidated Financial Statements. Credit Losses In June 2016, the FASB issued ASU No. 2016-13, Financial Instruments – Credit Losses (Topic 326) ("ASU 2016-13"). ASU 2016-13 implements an impairment model, known as the current expected credit loss model that is based on expected losses rather than incurred losses. Under the new guidance, an entity will recognize as an allowance its estimate of expected credit losses. ASU 2016-13 is effective for all interim and annual reporting periods beginning after December 15, 2019 and must be adopted using a modified retrospective approach, with certain exceptions. Early adoption is permitted. The Company does not expect the adoption of ASU 2016-13 to have a material impact on its Consolidated Financial Statements. Income Taxes In December 2019, the FASB issued ASU No. 2019-12, Income Taxes – Simplifying the Accounting for Income Taxes (“ASU 2019-12”). The guidance removes exceptions to the general principles in Income Taxes (Topic 740) for allocating tax expense between financial statement components, accounting basis differences stemming from an ownership change in foreign investments and interim period income tax accounting for year-to-date losses that exceed projected losses. The guidance becomes effective for annual reporting periods beginning after December 15, 2020 and interim periods within those fiscal years with early adoption permitted. The Company plans to adopt ASU 2019-12 effective January 1, 2020 and does not expect this adoption to have a material impact on its Consolidated Financial Statements.

Fair Value Measurement

Fair Value Measurement	12 Months Ended
	Dec. 31, 2019
Fair Value Disclosures [Abstract]
Fair Value Measurement	NOTE 2 – FAIR VALUE MEASUREMENT The Company measures certain assets and liabilities at fair value on a recurring basis, including cash equivalents, available-for-sale securities and the free share asset/liability. The accounting guidance establishes a three-tier hierarchy, which prioritizes the inputs used in the valuation methodologies in measuring fair value as follows: Level 1: Unadjusted quoted prices in active markets that are accessible at the measurement date for identical, unrestricted assets or liabilities; Level 2: Quoted prices in markets that are not active, or inputs which are observable, either directly or indirectly, for substantially the full term of the asset or liability; and Level 3: Prices or valuation techniques that require inputs that are both significant to the fair value measurement and unobservable ( i.e. supported by little or no market activity). The fair value measurements of the Company’s cash equivalents, available-for-sale securities and the free share asset/liability are identified at the following levels within the fair value hierarchy (in thousands): December 31, 2019 Fair Value Measurement Total Level 1 Level 2 Level 3 Assets: Cash equivalents: Money market funds $ 30,496 $ 30,496 $ — $ — Commercial paper securities 2,999 — 2,999 — Total 33,495 30,496 2,999 — Marketable securities: Commercial paper securities 155,368 — 155,368 — Corporate debt securities 95,017 — 95,017 — U.S. government-sponsored entity debt securities 53,493 — 53,493 — Total 303,878 — 303,878 — Total cash equivalents and marketable securities $ 337,373 $ 30,496 $ 306,877 $ — Free shares asset $ 236 $ — $ — $ 236 December 31, 2018 Fair Value Measurement Total Level 1 Level 2 Level 3 Assets: Cash equivalents: Money market funds $ 103,291 $ 103,291 $ — $ — Total 103,291 103,291 — — Marketable securities: Commercial paper securities 177,224 — 177,224 — Corporate debt securities 63,870 — 63,870 — U.S. government-sponsored entity debt securities 18,621 — 18,621 — Total 259,715 — 259,715 — Total cash equivalents and marketable securities $ 363,006 $ 103,291 $ 259,715 $ — Liabilities: Free shares liability $ 154 $ — $ — $ 154 Cash Equivalents and Marketable Securities The Company generally classifies its marketable securities and some cash equivalents as Level 2. Instruments are classified as Level 2 when observable market prices for identical securities that are traded in less active markets are used. When observable market prices for identical securities are not available, such instruments are priced using benchmark curves, benchmarking of like securities, sector groupings, matrix pricing and valuation models. These valuation models are proprietary to the pricing providers or brokers and incorporate a number of inputs, including in approximate order of priority: benchmark yields, reported trades, broker/dealer quotes, issuer spreads, two-sided markets, benchmark securities, bids, offers and reference data including market research publications. For certain security types, additional inputs may be used, or some of the standard inputs may not be applicable. Evaluators may prioritize inputs differently on any given day for any security based on market conditions, and not all inputs listed are available for use in the evaluation process for each security evaluation on any given day. Free Shares Asset/Liability As a result of the July 20, 2018 Share Purchase Agreement (“Sangamo France SPA”) to acquire Sangamo France (see Note 5 – Acquisition of Sangamo France ), the Company entered into arrangements with the holders of approximately 477,000 “free shares” of Sangamo France pursuant to which the Company has the right to purchase such shares from the holders (a call option) and such holders have the right to sell to the Company such shares from time to time through mid-2021 (a put option). The Company initially recorded a liability of $0.2 million on the acquisition date. The put options were classified within Level 3 of the fair value hierarchy as the Company utilized a binomial-lattice pricing model (the “Monte Carlo simulation model”) that involved certain market conditions to estimate the fair value of the options. The assumptions used in this simulation model are reviewed on a quarterly basis and adjusted, as needed. Subsequent changes in the fair value of the free shares are recorded in general and administrative expenses in the Consolidated Statements of Operations. During the year, the Company purchased approximately 111,000 shares of the 477,000 total free shares for a cash payment of approximately $0.3 million upon exercise of the put options. As of December 31, 2019, approximately 366,000 free shares remain outstanding and subject to purchase by the Company. The free shares liability was approximately $0.2 million at December 31, 2018 and the Company recognized a gain due to an increase in the fair value of the free shares of approximately $0.5 million for the year ended December 31, 2019, offset by approximately $0.1 million for the shares purchased during the year, bringing the balance to an asset of approximately $0.2 million at December 31, 2019. December 31, Free Shares valuation assumptions: 2019 2018 Sangamo Stock Price (USD) $ 8.68 $ 11.48 Sangamo France Stock Price (EUR) € 2.14 € 2.58 USD/ EUR Exchange Rate 0.91 0.87 Estimated Correlation Sangamo and Sangamo France Stock Prices 100.0 % — Sangamo Stock Price (USD) Volatility Estimate 72.5 % 79.9 % Sangamo France Stock Price (EUR) Volatility Estimate 72.5 % 8.6 % USD/ EUR Exchange Rate Volatility Estimate 6.6 % 7.7 % Risk Free Rate and Cost of Debt by Expected Exercise Date Varies Varies

Marketable Securities

Marketable Securities	12 Months Ended
	Dec. 31, 2019
Investments, Debt and Equity Securities [Abstract]
Marketable Securities	MARKETABLE SECURITIES The table below summarizes the Company’s cash equivalents and available-for-sale securities (in thousands): Amortized Gross Gross Estimated December 31, 2019 Cash equivalents: Money market funds $ 30,496 $ — $ — $ 30,496 Commercial paper securities 2,998 1 — 2,999 Total 33,494 1 — 33,495 Available-for-sale securities: Commercial paper securities 155,230 145 (7) 155,368 Corporate debt securities 94,905 115 (3) 95,017 U.S. government-sponsored entity debt securities 53,411 91 (9) 53,493 Total 303,546 351 (19) 303,878 Total cash equivalents and available-for-sale securities $ 337,040 $ 352 $ (19) $ 337,373 December 31, 2018 Cash equivalents: Money market funds $ 103,291 $ — $ — $ 103,291 Total 103,291 — — 103,291 Available-for-sale securities: Commercial paper securities 177,353 — (129) 177,224 Corporate debt securities 63,981 — (111) 63,870 U.S. government-sponsored entity debt securities 18,640 — (19) 18,621 Total 259,974 — (259) 259,715 Total cash equivalents and available-for-sale securities $ 363,265 $ — $ (259) $ 363,006 The fair value of investments available-for-sale by contractual maturity were as follows (in thousands): December 31, 2019 2018 Maturing in one year or less $ 282,046 $ 259,715 Maturing after one year through five years 21,832 — Total investments available-for-sale $ 303,878 $ 259,715 The Company had no material realized losses from the sale of available-for-sale securities for the years ended December 31, 2019, 2018 or 2017. Sangamo has the intent and ability to hold its investments for a period of time sufficient to allow for any anticipated recovery in market value. No investments were other-than-temporarily impaired at either December 31, 2019 or 2018.

Major Customers, Partnerships a

Major Customers, Partnerships and Strategic Alliances	12 Months Ended
	Dec. 31, 2019
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Major Customers, Partnerships and Strategic Alliances	NOTE 4 – MAJOR CUSTOMERS, PARTNERSHIPS AND STRATEGIC ALLIANCES Collaboration Agreements Kite In February 2018, the Company entered into a global collaboration and license agreement with Kite Pharma, Inc. (“Kite”), which became effective on April 5, 2018, and was amended and restated in September 2019, for the research, development and commercialization of potential engineered cell therapies for cancer. In this collaboration, Sangamo is working together with Kite on a research program under which the companies are designing zinc finger nucleases (“ZFNs”) and viral vectors to disrupt and insert certain genes in T-cells and natural killer cells (“NK-cells”) including the insertion of genes that encode chimeric antigen receptors (“CARs”), T-cell receptors (“TCRs”), and NK-cell receptors (“NKRs”) directed to mutually agreed targets. Kite is responsible for all clinical development and commercialization of any resulting products and has announced that they expect to initiate a clinical trial evaluating KITE-037, an allogeneic anti-CD19 CAR-T cell therapy, in 2020. Subject to the terms of this agreement, the Company granted Kite an exclusive, royalty-bearing, worldwide sublicensable license under the Company’s relevant patents and know-how to develop, manufacture and commercialize, for the purpose of treating cancer, specific cell therapy products that may result from the research program and that are engineered ex vivo using selected ZFNs and viral vectors developed under the research program to express CARs, TCRs or NKRs directed to candidate targets. During the research program term and subject to certain exceptions, except pursuant to this agreement, the Company is prohibited from researching, developing, manufacturing and commercializing, for the purpose of treating cancer, any cell therapy product that, as a result of ex vivo genome editing, expresses a CAR, TCR or NKR that is directed to a target expressed on or in a human cancer cell. After the research program term concludes and subject to certain exceptions, except pursuant to this agreement, the Company will be prohibited from developing, manufacturing and commercializing, for the purpose of treating cancer, any cell therapy product that, as a result of ex vivo genome editing, expresses a CAR, TCR or NKR that is directed to a candidate target. Following the effective date, in April 2018, the Company received a $150.0 million upfront payment from Kite. In addition, Kite will reimburse the Company’s direct costs to conduct service under the joint research program provisions of the agreement, and Kite will be responsible for all subsequent development, manufacturing and commercialization of any licensed products. Sangamo is also eligible to receive contingent development- and sales-based milestone payments that could total up to $3.01 billion if all of the specified milestones in this agreement are achieved. Of this amount, approximately $1.26 billion relates to the achievement of specified research, clinical development, regulatory and first commercial sale milestones, and approximately $1.75 billion relates to the achievement of specified sales-based milestones if annual worldwide net sales of licensed products reach specified levels. Each development- and sales-based milestone payment is payable (i) only once for each licensed product, regardless of the number of times that the associated milestone event is achieved by such licensed product, and (ii) only for the first ten times that the associated milestone event is achieved, regardless of the number of licensed products that may achieve such milestone event. In addition, the Company will be entitled to receive escalating, tiered royalty payments with a percentage in the single digits based on potential future annual worldwide net sales of licensed products. These royalty payments will be subject to reduction due to patent expiration, entry of biosimilar products to the market and payments made under certain licenses for third-party intellectual property. The initial research term of the agreement is six years. Kite has an option to extend the research term for up to two additional one The Company assessed the agreement with Kite in accordance with ASC Topic 606 and concluded that Kite is a customer. Kite has the right to terminate this agreement, in its entirety or on a per licensed product or per candidate target basis, for any reason after a specified notice period. Each party has the right to terminate this agreement on account of the other party’s bankruptcy or material, uncured breach. The Company has identified the primary performance obligations within the Kite agreement as: (1) a license to the technology along with the stand by ready obligation to perform research services, and (2) the on-going research services. Revenue from the upfront license fee relates to access to the license and Company’s obligation to stand-ready to perform such research services as additional targets are selected by Kite. As a result of this obligation to perform research services when and if requested throughout the duration of the contract, the fee for the license and the stand-ready obligation will be recognized over time on a straight-line basis through June 2024, the estimated period of the stand-ready obligation. Revenue from the reimbursable costs related to the integrated service deliverable is recognized as the research services are performed. Related costs and expenses under these arrangements have historically approximated the revenues recognized. The estimated period of performance and project cost is reviewed quarterly and adjusted, as needed, to reflect the Company’s current assumptions regarding the timing of its deliverables. As of December 31, 2019, and 2018 the Company had deferred revenue of $106.5 million and $131.5 million, respectively, related to this agreement. Revenues recognized under the agreement were as follows (in thousands): Year Ended December 31, 2019 2018 Revenue related to Kite agreement: Recognition of license and stand-ready fee $ 24,977 $ 18,545 Research services 9,373 6,972 Total $ 34,350 $ 25,517 Pfizer SB-525 Global Collaboration and License Agreement In May 2017, the Company entered into an exclusive, global collaboration and license agreement with Pfizer, pursuant to which it established a collaboration for the research, development and commercialization of SB-525, its gene therapy product candidate for hemophilia A, and closely related products. Under this agreement, the Company is responsible for conducting the Phase 1/2 clinical trial and certain manufacturing activities for SB-525, while Pfizer is responsible for subsequent worldwide development, manufacturing, marketing and commercialization of SB-525. Sangamo may also collaborate in the research and development of additional adeno-associated virus ("AAV") based gene therapy products for hemophilia A. The Company originally received an upfront fee of $70.0 million and is eligible to receive development milestone payments contingent on the achievement of specified clinical development, intellectual property, regulatory and first commercial sale milestones for SB-525 and potentially other products. In addition, Sangamo is eligible to receive up to $208.5 million in payments upon the achievement of specified clinical development, intellectual property and regulatory milestones and up to $266.5 million in payments upon first commercial sale milestones for SB-525 and potentially other products. The total amount of potential clinical development, intellectual property, regulatory, and first commercial sale milestone payments, assuming the achievement of all specified milestones in the hemophilia A Pfizer agreement, is up to $475.0 million, which includes up to $300.0 million for SB-525 and up to $175.0 million for other products that may be developed under the agreement, subject to reduction on account of payments made under certain licenses for third party intellectual property. In addition, Pfizer agreed to pay the Company royalties for each potential licensed product developed under the agreement based on an escalating tiered, double-digit percentage of the annual net sales of such product. These royalties are subject to reduction due to patent expiration, entry of biosimilar products to the market and payment made under certain licenses for third-party intellectual property. To date, a $25.0 million milestone has been achieved, however no products have been approved and therefore no royalty fees have been earned under the hemophilia A Pfizer agreement. The Company assessed the agreement with Pfizer in accordance with ASC Topic 606 and concluded that Pfizer is a customer. As of December 31, 2019, the total transaction price under this agreement is $105.0 million, which represents the upfront and research services fees of $80.0 million and one unconstrained milestone in the amount of $25.0 million. Sangamo is responsible for internal and external research costs as part of the upfront fee and has the ability to request additional reimbursement from Pfizer if certain conditions are met. None of the clinical or regulatory milestones have been included in the transaction price, as all such milestone amounts are fully constrained. As part of its evaluation of the constraint, the Company considered numerous factors, including the fact that achievement of the milestones at this time is uncertain and contingent upon future periods when the uncertainty related to the variable consideration is resolved. The Company will re-evaluate the transaction price, including its estimated variable consideration included in the transaction price and all constrained amounts in each reporting period and as uncertain events are resolved or other changes in circumstances occur. Subject to the terms of the agreement, the Company granted Pfizer an exclusive worldwide royalty-bearing license, with the right to grant sublicenses, to use certain technology controlled by the Company for the purpose of developing, manufacturing and commercializing SB-525 and related products. Pfizer granted the Company a non-exclusive, worldwide, royalty free, fully paid license, with the right to grant sublicenses, to use certain manufacturing technology developed under the agreement and controlled by Pfizer to manufacture the Company’s products that utilize the AAV delivery system. During a specified period, neither the Company nor Pfizer will be permitted to clinically develop or commercialize, outside of the collaboration, certain AAV-based gene therapy products for hemophilia A. Unless earlier terminated, the agreement has a term that continues on a per product and per country basis until the later of (i) the expiration of patent claims that cover the product in a country, (ii) the expiration of regulatory exclusivity for a product in a country, and (iii) 15 years after the first commercial sale of a product in a country. Pfizer has the right to terminate the agreement without cause in its entirety or on a per product or per country basis. The agreement may also be terminated by either party based on an uncured material breach by the other party or the bankruptcy of the other party. Upon termination for any reason, the license granted by the Company to Pfizer to develop, manufacture and commercialize SB-525 and related products will automatically terminate. Upon termination by the Company for cause or by Pfizer in any country or countries, Pfizer will automatically grant the Company an exclusive, royalty-bearing license under certain technology controlled by Pfizer to develop, manufacture and commercialize SB-525 in the terminated country or countries. The Company has identified one performance obligation within the hemophilia A Pfizer agreement as a license to the technology and on-going research services. The Company concluded that the license is not discrete, as it does not have stand-alone value to Pfizer apart from the research services to be performed by the Company pursuant to the agreement. As a result, the Company recognizes revenue from the upfront payment based on proportional performance of the on-going services through 2020, the estimated period the Company will perform research services. The estimate of progress towards the satisfaction of its performance obligation and project cost is reviewed quarterly and adjusted, as needed, to reflect the Company’s current assumptions regarding the timing of its deliverables. As of December 31, 2019 and 2018, the Company had deferred revenue of $4.0 million and $10.0 million, respectively, related to this agreement. In December 2019, the Company entered into an amendment to the collaboration agreement, pursuant to which the Company transferred the IND for SB-525 to Pfizer. Upon this transfer the Company achieved a $25.0 million milestone as the conditions for achieving the milestone were met. The Company recognized approximately $23.7 million attributed to this milestone as revenue during the year ended December 31, 2019. The balance of this payment of $1.3 million will be recognized as revenue commensurate with the provision of research services over the remaining term of the agreement. Revenues recognized under the agreement were as follows (in thousands): Year Ended December 31, 2019 2018 2017 Revenue related to Pfizer SB-525 agreement: Recognition of upfront fee and research services $ 15,697 $ 37,810 $ 17,008 Milestone achievement 23,662 — — Total $ 39,359 $ 37,810 $ 17,008 The Company adopted ASC Topic 606 effective January 1, 2018, using the modified retrospective method. The impact on the hemophilia A Pfizer agreement was to increase the amount of the recognition of the up-front payment by approximately $5.2 million. This amount resulted in a decrease to the opening balance of accumulated deficit and a decrease to deferred revenues, respectively. In the first quarter of 2019, the Company updated its estimated project cost and related revenues under this program. This adjustment was a direct result of the increase in project scope during the first quarter of 2019 and the corresponding costs, which resulted in a decrease in the measure of proportional performance. In December 2019, the Company updated its estimated project cost and related revenues upon transfer of the IND for SB-525 to Pfizer. This adjustment was a direct result of the decrease in project scope during the fourth quarter of 2019 and the corresponding costs, which resulted in an increase in the measure of proportional performance. During the year ended December 31, 2019, the Company recognized $15.7 million in revenues related to the Pfizer SB-525 agreement, which included approximately $8.7 million acceleration in revenues recorded in the three months ended December 31, 2019 related to the updated estimated project cost, offset by approximately $3.0 million reduction in revenues recorded in the three months ended March 31, 2019 related to the updated estimated project cost. C9ORF72 Research Collaboration and License Agreement In December 2017, the Company entered into a separate exclusive, global collaboration and license agreement with Pfizer for the development and commercialization of potential gene therapy products that use ZFP transcription factors (“TFs”) to treat amyotrophic lateral sclerosis (“ALS”) and frontotemporal lobar degeneration (“FTLD”) linked to mutations of the C9ORF72 gene. Pursuant to this agreement, the Company agreed to work with Pfizer on a research program to identify, characterize and preclinically develop ZFP-TFs that bind to and specifically reduce expression of the mutant form of the C9ORF72 gene. The Company received a $12.0 million upfront payment from Pfizer and is eligible to receive up to $60.0 million in development milestone payments from Pfizer contingent on the achievement of specified preclinical development, clinical development and first commercial sale milestones, and up to $90.0 million commercial milestone payments if annual worldwide net sales of the licensed products reach specified levels. In addition, Pfizer will pay the Company royalties based on an escalating tiered, mid- to high-single digit percentage of the annual worldwide net sales of the licensed products. These royalty payments are subject to reduction due to patent expiration, entry of biosimilar products to the market and payments made under certain licenses for third party intellectual property. Each party will be responsible for the cost of its performance of the research program. Pfizer will be operationally and financially responsible for subsequent development, manufacturing and commercialization of the licensed products. The Company assessed the agreement with Pfizer in accordance with ASC Topic 606 and concluded that Pfizer is a customer. The Company concluded the total transaction price under this agreement is $12.0 million, which represents the upfront fee. None of the clinical or regulatory milestones have been included in the transaction price, as all milestone amounts are fully constrained. As part of its evaluation of the constraint, the Company considered numerous factors, including the fact that achievement of the milestones at this time is uncertain and contingent upon future periods when the uncertainty related to the variable consideration is resolved. The Company will re-evaluate the transaction price, including its estimated variable consideration included in the transaction price and all constrained amounts, in each reporting period and as uncertain events are resolved or other changes in circumstances occur. Subject to the terms of this agreement, the Company granted Pfizer an exclusive, royalty-bearing, worldwide license under the Company’s relevant patents and know-how to develop, manufacture and commercialize gene therapy products that use resulting ZFP-TFs that satisfy pre-agreed criteria. During a specified period, neither the Company nor Pfizer will be permitted to research, develop, manufacture or commercialize outside of the collaboration any ZFPs that specifically bind to the C9ORF7 2 gene. Unless earlier terminated, the agreement has a term that continues on a per licensed product and per country basis until the later of (i) the expiration of patent claims that cover the licensed product in a country, (ii) the expiration of regulatory exclusivity for a licensed product in a country, and (iii) 15 years after the first commercial sale of a licensed product in a major market country. Pfizer also has the right to terminate the agreement without cause in its entirety or on a per product or per country basis. The agreement may also be terminated by either party based on an uncured material breach by the other party or the bankruptcy of the other party. The agreement will also terminate if the Company is unable to identify any lead candidates for development within a specified period of time or if Pfizer elects not to advance a lead candidate beyond a certain development milestone within a specified period of time. Upon termination for any reason, the license granted by the Company to Pfizer to develop, manufacture and commercialize licensed products under the agreement will automatically terminate. Upon termination by the Company for cause or by Pfizer without cause for any licensed product or licensed products in any country or countries, the Company will have the right to negotiate with Pfizer to obtain a non-exclusive, royalty-bearing license under certain technology controlled by Pfizer to develop, manufacture and commercialize the licensed product or licensed products in the terminated country or countries. Following termination by the Company for Pfizer’s material breach, Pfizer will not be permitted to research, develop, manufacture or commercialize ZFPs that specifically bind to the C9ORF72 gene for a period of time. Following termination by Pfizer for the Company’s material breach, the Company will not be permitted to research, develop, manufacture or commercialize ZFPs that specifically bind to the C9ORF72 gene for a period of time. The Company has identified the performance obligation within this agreement as a license to the technology and on-going research services. The Company concluded that the license is not discrete as it does not have stand-alone value to Pfizer apart from the services to be performed by the Company pursuant to the agreement. As a result, the Company recognizes revenue from the upfront payment based on proportional performance of the on-going services over the estimated period the Company will perform research services. The estimation of progress towards the satisfaction of its performance obligation and project cost is reviewed quarterly and adjusted, as needed, to reflect the Company’s current assumptions regarding the timing of its deliverables. As of December 31, 2019 and 2018, the Company had deferred revenue of $8.0 million and $9.8 million, respectively, related to this agreement. Revenues recognized under the agreement were as follows (in thousands): Year Ended December 31, 2019 2018 2017 Recognition of upfront fee related to Pfizer C9ORF72 agreement $ 1,827 $ 2,188 $ — Sanofi In January 2014, the Company entered into an exclusive worldwide collaboration and license agreement with Bioverativ Inc., (now Sanofi Genzyme, a global business unit of Sanofi S.A. (“Sanofi”)), to develop therapeutics for hemoglobinopathies, focused on beta thalassemia and sickle cell disease (“SCD”). The agreement was originally signed with Biogen MA Inc., who subsequently assigned it to Bioverativ Inc., which was later acquired by Sanofi. Under the agreement, the Company is jointly conducting two research programs: the beta thalassemia program and the SCD program. In the beta thalassemia program, the Company is responsible for all discovery, research and development activities through the first human clinical trial. In the SCD program, both parties are responsible for research and development activities through the submission of an IND application for ZFP therapeutics intended to treat SCD. Under both programs, Sanofi is responsible for subsequent worldwide clinical development, manufacturing and commercialization of licensed products developed under the agreement. At the end of the specified research terms for each program or under certain specified circumstances, Sanofi has the right to step in and take over any of the Company’s remaining activities. Furthermore, the Company has an option to co-promote in the U.S. any licensed products to treat beta thalassemia and SCD developed under the agreement, and Sanofi will compensate the Company for such co-promotion activities. Subject to the terms of the agreement, the Company has granted Sanofi an exclusive, royalty-bearing license, with the right to grant sublicenses, to use certain ZFP and other technology controlled by the Company for the purpose of researching, developing, manufacturing and commercializing licensed products developed under the agreement. The Company also granted Sanofi a non-exclusive worldwide, royalty-free fully paid license with the right to grant sublicenses, under the Company’s interest in certain other intellectual property developed pursuant to the agreement. During the term of the agreement, the Company is not permitted to research, develop, manufacture or commercialize, outside of the agreement, certain gene therapy products that target genes relevant to the licensed products. Under the agreement, the Company received an upfront license fee of $20.0 million and is eligible to receive development and sales milestone payments upon the achievement of specified regulatory, clinical development and sales milestones. In addition, the Company will also be eligible to receive up to $115.8 million in payments upon the achievement of specified clinical development and regulatory milestones, as well as up to $160.5 million in payments upon the achievement of specified sales milestones. The total amount of potential regulatory, clinical development, and sales milestone payments, assuming the achievement of all specified milestones in the agreement, is up to $276.3 million. In addition, the Company will receive royalty payments for each licensed product that are a tiered double-digit percentage of annual net sales of each product. Sanofi reimburses Sangamo for agreed upon costs incurred in connection with research and development activities conducted by Sangamo. To date, a $6.0 million milestone has been achieved related to ST-400 for beta thalassemia and another $7.5 million milestone has been achieved related to SCD, however no products have been approved and therefore no royalty fees have been earned under the Sanofi agreement. The agreement may be terminated by (i) the Company or Sanofi for the uncured material breach of the other party, (ii) the Company or Sanofi for the bankruptcy or other insolvency proceeding of the other party; (iii) Sanofi, upon 180 days’ advance written notice to the Company and (iv) Sanofi, for certain safety reasons upon written notice to, and after consultation with, the Company. As a result, actual future milestone payments could be lower than the amounts stated above. All contingent payments under the agreement, when earned, will be non-refundable and non-creditable. The transaction price as of December 31, 2019 of $89.2 million includes the upfront license fee of $20.0 million, milestones of $13.5 million achieved to date and $55.7 million of estimated research service fees for identified research projects over the estimated performance period, as all unachieved milestone amounts are fully constrained. As part of its evaluation of the constraint, the Company considered numerous factors, including the fact that achievement of the milestones at this time is uncertain and contingent upon future periods when the uncertainty related to the variable consideration is resolved. The Company will re-evaluate the transaction price, including the estimated variable consideration included in the transaction price and all constrained amounts, in each reporting period and as uncertain events are resolved or other changes in circumstances occur. None of the clinical or regulatory milestones have been included in the transaction price. The Company assessed the agreement with Sanofi in accordance with ASC Topic 606 and concluded that Sanofi is a customer. The Company has identified the performance obligations within this arrangement as a license to the technology and on-going research services activities. The Company concluded that the license is not discrete as it does not have stand-alone value to Sanofi apart from the research services to be performed pursuant to the agreement. As a result, the Company recognizes revenue from the upfront payment based on proportional performance of the ongoing services through 2022, the estimated period the Company will perform research services. The estimate of progress towards the satisfaction of performance obligation and project cost is reviewed quarterly and adjusted, as needed, to reflect the Company’s current assumptions regarding the timing of its deliverables. Revenue from the reimbursable costs related to the integrated service deliverable is recognized as the research services are performed. Related costs and expenses under these arrangements have historically approximated the revenues recognized. As of December 31, 2019 and 2018, the Company had deferred revenue of $1.7 million and $4.6 million, respectively, related to this agreement. In August 2019, the Company achieved a $6.0 million milestone with Sanofi upon dosing of the third subject in the ST-400 beta thalassemia Phase 1 clinical trial. The Company recognized approximately $5.7 million attributed to this milestone as revenue during the year ended December 31, 2019. In December 2019, the Company achieved a $7.5 million milestone with Sanofi upon dosing of the first subject in the SCD Phase 1 clinical trial. The Company recognized approximately $7.1 million attributed to this milestone as revenue during the year ended December 31, 2019. Revenues recognized under the agreement were as follows (in thousands): Year Ended December 31, 2019 2018 2017 Revenue related to Sanofi agreement: Recognition of upfront fee $ 3,494 $ 4,013 $ 1,769 Research services 6,367 9,503 10,489 Milestone achievement 12,819 — — Total $ 22,680 $ 13,516 $ 12,258 The Company adopted ASC Topic 606 effective January 1, 2018, using the modified retrospective method. The impact on the Sanofi agreement was to reduce the amount of the recognition of the up-front payment by approximately $4.1 million. This amount resulted in an increase to the opening balance of accumulated deficit and an increase to deferred revenues. California Institute for Regenerative Medicine In May 2018, the California Institute for Regenerative Medicine (“CIRM”) granted a Strategic Partnership Award for $8.0 million to fund the clinical studies of a potentially curative ZFP therapeutic for the treatment of beta thalassemia based on the application of Sangamo’s ZFN genome editing technology. The grant exists through December 31, 2022 and provides matching funds to support the evaluate ST-400, a gene-edited cell therapy candidate for people with transfusion-dependent beta thalassemia. As of December 31, 2019, the Company had received $5.2 million under the award. Under the terms of the CIRM grants, the Company is obligated to pay royalties and licensing fees based on a low single digit royalty percentage on net sales of CIRM-funded product candidates or CIRM-funded technology. The Company has the option to decline any and all amounts awarded by CIRM and as an alternative to revenue sharing, the Company has the option to convert the award to a loan. No such election has been made as of the date of the issuance of these financial statements. In the event that the Company terminates a CIRM-funded clinical trial, it will be obligated to repay the remaining CIRM funds on hand. As of December 31, 2019 and 2018, $5.7 million and $1.8 million, respectively, including accrued interest, related to this award is recorded as a loan in other long-term liabilities on the Consolidated Balance Sheets. Amended Collaboration and License Agreement with Takeda In January 2012, the Company entered into a collaboration and license agreement with Shire International GmbH, a wholly-owned subsidiary of Takeda Pharmaceutical Company Limited (“Takeda”), to research, develop and commercialize a ZFP therapeutic for treating Huntington’s disease. The Company received an upfront license fee of $13.0 million. In 2014, Sangamo recognized a $1.0 million milestone payment related to the hemophilia program. Takeda does not have any milestone payment obligations, but is required to pay single digit percentage royalties to the Company, up to a specified maximum cap, on the commercial sales of therapeutic products for Huntington’s disease. The Company is required to pay single digit percentage royalties to Takeda, up to a specified maximum cap, on commercial sales of therapeutic products from programs returned under the original agreement (which include blood clotting Factors VIII and IX) that use two zinc fingers. Pursuant to the agreement, the Company granted Takeda an exclusive, world-wide, royalty-bearing license, with the right to grant sublicenses, to use the Company’s ZFP technology for the purpose of developing and commercializing human therapeutic and diagnostic products for the Huntingtin gene (“ HTT gene”). During the term of the agreement, the Company is not permitted to research, develop or commercialize, outside of the agreement, certain products that target the HTT gene. The agreement may be terminated by (i) the Company or Takeda, in whole or in part, for the uncured material breach of the other party, (ii) the Company or Takeda for the bankruptcy or other insolvency proceeding of the other party and (iii) Takeda, in its entirety, effective upon at least 90 days’ advance written notice. The Company assessed the agreement with Takeda in accordance with ASC Topic 606 and concluded that Takeda is a customer. The Company has concluded that the license is not a separate unit of accounting as it does not have stand-alone value to Takeda apart from the research services to be performed pursuant to the Takeda agreement. The Company satisfied the deliverables and research services responsibilities within the amended arrangement which were completed in 2017. As a result, the Company recognized the remaining $2.3 million of deferred revenue from the upfront payment during the year ended December 31, 2017. Revenues recognized unde

Acquisition of Sangamo France

Acquisition of Sangamo France	12 Months Ended
	Dec. 31, 2019
Business Combinations [Abstract]
Acquisition of Sangamo France	NOTE 5 – ACQUISITION OF SANGAMO FRANCE On July 20, 2018, Sangamo entered into various agreements with the goal of eventually acquiring 100% of Sangamo France’s share capital. The Company entered into the Sangamo France SPA with certain shareholders of Sangamo France, pursuant to which it acquired 13,519,036 ordinary shares of Sangamo France (“Ordinary Shares”) as part of a block transaction that closed on October 1, 2018 (the “Acquisition Date”). Additionally, the Company and Sangamo France entered into a Tender Offer Agreement pursuant to which Sangamo agreed to acquire 11,528,635 Ordinary Shares for the same price per share as the Sangamo France SPA via a cash tender offer that closed on November 23, 2018. Following the block transaction, cash tender offer, and other open market purchases of shares, the Company owned 98.2% of the Ordinary Shares as of December 31, 2018 (or 25,047,671 Ordinary Shares). In addition to the Sangamo France SPA and the tender offer agreement, the Company also entered into arrangements with the holders of approximately 477,000 “free shares” of Sangamo France pursuant to which the Company has the right to purchase such shares from the holders (a call option) and such holders have the right to sell to the Company such shares from time to time through mid-2021 (a put option) (collectively the “Free Shares Options”). In June 2019, Sangamo France became a société par actions simplifiée (“S.A.S.”) and was renamed from “TxCell” to “Sangamo Therapeutics France.” During 2019, the Company acquired approximately 111,000 vested free shares, increasing its ownership of the Ordinary Shares to 98.7% as of December 31, 2019. At the Acquisition Date, the fair value of the Free Shares Options was estimated to be a liability of $0.2 million. See Note 2 - Fair Value Measurement – Free Shares Asset/Liability for information regarding the valuation method. The fair value of the Free Shares Options will vary based on future changes in the Company’s stock price during the option period. The fair value of the Free Shares Options was estimated to be an asset of $0.2 million as of December 31, 2019. The acquisition of Sangamo France was accounted for as a business combination in accordance with ASC Topic 805, Business Combinations . The operating results of Sangamo France after the Acquisition Date have been included in the Company’s Consolidated Statements of Operations. There were no purchase price adjustments subsequent to the acquisition. There were no goodwill impairments during the years ended December 31, 2019 or 2018 and, as noted below, substantially all of the non-controlling interest on the Acquisition Date was subsequently acquired by the Company and, accordingly, substantially all of the goodwill is allocated to the Company as of December 31, 2019 and 2018. The following table summarizes the estimated consideration transferred and the fair value of the net assets acquired as of the Acquisition Date (in thousands): October 1, 2018 Consideration transferred $ 45,911 Fair value of non-controlling interest 35,829 Fair value of Sangamo France $ 81,740 Cash $ 4,779 Current assets 2,427 Property and equipment 1,857 IPR&D 55,019 Other assets 155 Current liabilities (9,761) Assumed debt liabilities (4,933) Deferred tax liability, net (6,798) Fair value of net identifiable assets acquired 42,745 Goodwill 38,995 Total fair value of net assets acquired $ 81,740 Non-controlling Interest The fair value of the non-controlling interest at the Acquisition Date was based on the $2.99 acquisition price per share for the 11,981,867 Ordinary Shares that were not purchased by the Company in the block transaction on the Acquisition Date. Subsequent to the Acquisition Date and through December 31, 2018, the Company acquired 11,528,635 Ordinary Shares, which when aggregated with the 13,519,036 Ordinary Shares acquired at the Acquisition Date, resulted in the Company owning 98.2% of all Ordinary Shares as of December 31, 2018. During 2019, the Company acquired approximately 111,000 vested free shares for approximately $0.3 million of cash, pursuant to the exercise of the Free Shares Options, increasing its ownership of the Ordinary Shares to 98.7% as of December 31, 2019. Non-controlling interest as of December 31, 2019 was as follows (in thousands): Total Balance, beginning of year $ 739 Fair value of additional shares acquired (321) Loss attributable to non-controlling interest (233) Balance, end of year $ 185

Other Balance Sheet Details

Other Balance Sheet Details	12 Months Ended
	Dec. 31, 2019
Balance Sheet Related Disclosures [Abstract]
Supplemental Balance Sheet Disclosures	NOTE 6 – OTHER BALANCE SHEET DETAILS Property and Equipment, Net Property and equipment, net consist of the following (in thousands): December 31, 2019 2018 Laboratory equipment $ 17,179 $ 11,466 Furniture and fixtures 4,639 3,840 Leasehold improvements 13,888 3,640 Buildings — 3,876 Construction in progress 5,901 65,211 41,607 88,033 Less: accumulated depreciation and amortization (11,681) (9,310) Property and equipment, net $ 29,926 $ 78,723 Depreciation and amortization expense was $3.9 million in 2019, $2.4 million in 2018 and $1.5 million in 2017. Intangible Assets The changes in intangible assets were as follows (in thousands): December 31, 2019 2018 Balance, beginning of year $ 54,243 $ — Indefinite-lived assets - IPR&D — 55,019 Foreign currency translation adjustment (1,087) (776) Balance, end of year $ 53,156 $ 54,243 Goodwill The changes in goodwill were as follows (in thousands): December 31, 2019 2018 Balance, beginning of year $ 40,044 $ 1,585 Goodwill acquired — 38,995 Foreign currency translation adjustment (771) (536) Balance, end of year $ 39,273 $ 40,044 Accounts Payable and Accrued Liabilities Accounts payable and accrued liabilities consist of the following (in thousands): December 31, 2019 2018 Accounts payable $ 6,671 $ 3,355 Accrued research and development expenses 4,102 10,999 Operating lease liabilities - current 3,214 — Accrued professional fees 1,118 1,930 Deferred rent — 204 Other 2,451 4,969 Total accounts payable and accrued liabilities $ 17,556 $ 21,457

Commitments and Contingencies

Commitments and Contingencies	12 Months Ended
	Dec. 31, 2019
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	NOTE 7 – COMMITMENTS AND CONTINGENCIES Leases Sangamo occupies approximately 87,700 square feet of office and research and development laboratory facilities in Brisbane, California pursuant to a lease that expires in May 2029. Sangamo also occupies approximately 45,600 square feet of research and office space in Richmond, California pursuant to leases that expire in August 2026. In addition, the Company leases approximately 20,800 square feet of office and research space in Valbonne, France subject to leases that expire beginning in June 2025 through March 2028. Certain of these leases also include renewal options at the election of the Company to renew or extend the lease for an additional five With respect to the Brisbane lease, the commencement date for approximately 35,080 square feet of the office space occurred in January 2019 while the commencement date for the remaining approximately 52,620 square feet occurred in June 2019. The Company has the right and exercised that right to make tenant improvements, including the addition of laboratory space, with a lease incentive allowance of $6.8 million on the first portion of the space occupied and $10.2 million on the portion of the lease that commenced in June 2019. As of December 31, 2019, these incentives have been received and used. The Company performed evaluations of its contracts and determined each of its identified leases are operating leases. For the year ended December 31, 2019, the Company incurred $7.9 million of lease costs included in operating expenses in the Consolidated Statement of Operations in relation to these operating leases. Variable lease expense was $1.9 million for the year ended December 31, 2019 and was not included in the measurement of the Company’s operating ROU assets and lease liabilities. The variable expense consists primarily of the Company’s proportionate share of operating expenses, property taxes and insurance and is classified as lease expense due to the Company’s election to not separate lease and non-lease components. Cash paid for amounts included in the measurement of operating lease liabilities for the year ended December 31, 2019 was $3.5 million and was included in net cash used in operating activities in the Company’s Consolidated Statement of Cash Flow. Rent expense related to lease agreements was $7.9 million, $2.3 million, and $1.1 million for 2019, 2018 and 2017, respectively. Future minimum payments under lease obligations at December 31, 2019 consist of the following (in thousands): Total 2020 $ 5,870 2021 6,390 2022 6,468 2023 6,556 2024 6,694 Thereafter 26,141 Total lease payments 58,119 Less: Imputed interest (13,713) Total $ 44,406 Reported as of December 31, 2019: Operating lease liabilities - current (included in Accounts payable and accrued liabilities on the Consolidated Balance Sheet) $ 3,214 Operating lease liabilities - long-term 41,192 Total $ 44,406 As of December 31, 2019, the weighted-average remaining lease term is 8.8 years and the weighted-average incremental borrowing rate used to determine the operating lease liability was 6.2% for the Company’s operating leases. Contractual Commitments As of December 31, 2019, the Company has manufacturing obligations that include a fee of $6.3 million for dedicated capacity pursuant to the Development and Manufacturing Services Agreement with Brammer Bio MA, now a Thermo Fisher Scientific Inc. subsidiary ("Brammer"). The Company also has an Option Agreement ("Option") with Brammer, entered in April 2019, whereby Brammer granted the Company an option to secure dedicated capacity for manufacturing in Brammer’s facilities. The Company paid $3.0 million for the Option, which expires on December 31, 2021. In addition, the Company agreed to pay Brammer $2.0 million, $0.5 million of which was paid upon execution of the agreement, to assist it in establishing its manufacturing capabilities in Brisbane, California, which may increase Sangamo's contractual commitments in the future. Furthermore, the Company has non-cancelable contractual commitments under manufacturing-related supplier arrangements with Brammer, which requires minimum purchase commitments totaling approximately $2.5 million through December 2021, $0.5 million of which was paid upon execution of the agreement. The Company also has $1.2 million of license obligations related to its intellectual property. Contingencies Sangamo is not party to any material pending legal proceeding. From time to time, Sangamo may be involved in legal proceedings arising in the ordinary course of business.

Stockholders' Equity

Stockholders' Equity	12 Months Ended
	Dec. 31, 2019
Equity [Abstract]
Stockholders' Equity	NOTE 8 – STOCKHOLDERS’ EQUITY Preferred Stock The Company has 5,000,000 preferred shares authorized, which may be issued at the discretion of the Company’s Board of Director’s discretion. Common Stock In April 2019, Sangamo completed an underwritten public offering of its common stock, in which the Company sold an aggregate of 12.7 million shares of its common stock at a public offering price of $11.50 per share. The net proceeds to Sangamo from the sale of shares in this offering, after deducting underwriting discounts and commissions and other offering expenses, were approximately $136.3 million. In April 2018, Sangamo completed an underwritten public offering of its common stock, in which the Company sold an aggregate of 14.2 million shares of its common stock at a public offering price of $16.25 per share. The net proceeds to Sangamo from the sale of shares in this offering, after deducting underwriting discounts and commissions and other offering expenses, were approximately $215.8 million. In June 2017, Sangamo completed an underwritten public offering of its common stock, in which the Company sold an aggregate of 11.5 million shares of its common stock at a public offering price of $7.25 per share. The net proceeds to Sangamo from the sale of shares in this offering, after deducting underwriting discounts and commissions and other offering expenses, were approximately $78.1 million. Stock Incentive Plan In April 2018, the Compensation Committee of the Company’s Board of Directors approved the Sangamo Therapeutics, Inc. 2018 Equity Incentive Plan (the “2018 Plan”), subject to approval by the Company’s stockholders. The 2018 Plan became effective on June 11, 2018 upon approval at the Company’s Annual Meeting of Stockholders. In connection with the approval of the 2018 Plan, no additional equity awards will be granted under the 2013 Plan, however all outstanding equity awards under the 2013 Plan will continue to be subject to the terms and conditions as set forth in the agreements evidencing such awards and the terms of the 2013 Plan. The exercise price of a stock option granted under the 2018 Plan may not be less than 100% of the fair market value of the Company's common stock subject to the stock option on the date of grant, and the option term will not exceed 10 years. If the person to whom the stock option is granted is a 10% stockholder of the Company, and the stock option granted qualifies as an incentive stock option, then the exercise price per share will not be less than 110% of the fair market value of the Company’s common stock on the date of grant, and the option term will not exceed five years. Generally, stock options granted under the 2018 Plan vest over four years at a rate of 25% on the one year anniversary of the date of grant and 1/48 per month thereafter and expire 10 years after the date of grant, or earlier upon termination of employment or services to the Company. The number of shares of common stock reserved for issuance under the 2018 Plan will be reduced: (i) on a 1-for-1 basis for each share of common stock subject to a stock option or stock appreciation right granted under the plan, (ii) by a fixed ratio of 1.33 shares of common stock for each share of common stock issued pursuant to a full-value award granted under the plan. Shares subject to any outstanding stock options or other awards under the 2018 Plan that expire or otherwise terminate prior to the issuance of the shares subject to those stock options or awards will be available for subsequent issuance under the 2018 Plan. Any unvested shares issued under the 2018 Plan that the Company subsequently purchases, pursuant to repurchase rights under the 2018 Plan, will be added back to the number of shares reserved for issuance under the 2018 Plan on a 1-for-1 basis or a 1.33-for-1 basis (depending on the ratio at which the share reserve was debited for the original award) and will accordingly be available for subsequent issuance in accordance with the terms of the 2018 Plan. Employee Stock Purchase Plan In June 2018, the Company’s stockholders approved the amendment and restatement of the ESPP. As amended, the ESPP provides a total reserve of 4.6 million shares of common stock for issuance under the ESPP. Eligible employees may purchase common stock at 85% of the lesser of the fair market value of the Company’s common stock on the first day of the applicable two six Stock Option Activity A summary of Sangamo’s stock option activity is as follows: Number of Weighted- Weighted-Average Aggregate (In years) (In thousands) Options outstanding at December 31, 2018 8,726,092 $ 11.23 Options granted 4,530,288 $ 9.68 Options exercised (806,226) $ 5.08 Options canceled (2,620,867) $ 12.39 Options outstanding at December 31, 2019 9,829,287 $ 10.71 7.91 $ 7,472 Options vested and expected to vest at December 31, 2019 9,829,287 $ 10.71 7.91 $ 7,472 Options exercisable at December 31, 2019 3,993,645 $ 10.43 6.54 $ 5,442 Newly created shares are issued upon exercises of options. There were no shares subject to Sangamo’s right of repurchase as of December 31, 2019. The intrinsic value of options exercised was $4.7 million, $27.0 million and $12.3 million during 2019, 2018 and 2017, respectively. At December 31, 2019, the aggregate intrinsic values of outstanding and exercisable options were $7.5 million and $5.4 million, respectively. The aggregate intrinsic value of options vested and expected to vest as of December 31, 2019, 2018 and 2017 was $7.5 million, $24.5 million and $71.7 million, respectively. Restricted Stock Units During 2019, 2018 and 2017, the Company awarded 834,745, 346,055, and 12,600 RSUs, respectively. The RSUs awarded in 2019, 2018 and 2017 had an average grant date fair value per award of $9.49, $17.87 and $15.85, respectively. These awards generally vest in a series of three successive equal annual installments. The aggregate fair value of RSUs vested during 2019, 2018 and 2017 was $2.0 million, $0.6 million and $1.2 million, respectively. A summary of Sangamo’s RSU activity is as follows: Number of Weighted-Average Aggregate Intrinsic (In years) (In thousands) RSUs outstanding at December 31, 2018 322,701 RSUs awarded 834,745 RSUs released (118,807) RSUs forfeited (175,789) RSUs outstanding at December 31, 2019 862,850 1.22 $ 7,222 RSUs vested and expected to vest at December 31, 2019 862,850 1.22 $ 7,222 RSUs that vested in 2019, 2018 and 2017 were net-share settled such that the Company withheld shares with value equivalent to the employees’ minimum statutory obligation for the applicable income and other employment taxes, and remitted the cash to the appropriate taxing authorities. The total shares withheld were approximately 39,160, 20,193, and 42,243 for 2019, 2018 and 2017, respectively, and were based on the value of the RSUs on their respective issuance dates as determined by the Company’s closing stock price. Total payments for the employees’ tax obligations to taxing authorities were $0.4 million , $0.3 million and $0.7 million in 2019, 2018 and 2017, respectively and are reflected as a financing activity within the accompanying Consolidated Statements of Cash Flows. These net-share settlements had the effect of share repurchases by the Company as they reduced and retired the number of shares that would have otherwise been issued as a result of the vesting and did not represent an expense to the Company. As of December 31, 2019, there were 6,691,209 shares reserved for future awards under the Company’s 2018 Plan and 2,757,600 shares of common stock reserved for future issuance under the ESPP.

Stock-Based Compensation

Stock-Based Compensation	12 Months Ended
	Dec. 31, 2019
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Stock-Based Compensation	NOTE 9 – STOCK-BASED COMPENSATION The following table shows total stock-based compensation expense recognized in the accompanying Consolidated Statements of Operations (in thousands): Year Ended December 31, 2019 2018 2017 Research and development $ 10,135 $ 8,249 $ 5,031 General and administrative 9,195 6,428 4,058 Total stock-based compensation expense $ 19,330 $ 14,677 $ 9,089 As of December 31, 2019, total stock-based compensation expense to be recognized in future periods related to unvested stock options was $37.4 million, which is expected to be expensed over a weighted-average period of 2.76 years. As of December 31, 2019, total stock-based compensation expense to be recognized in future periods related to unvested RSUs was $7.0 million, which is expected to be expensed over a weighted-average period of 2.11 years. There was no capitalized stock-based employee compensation expense as of December 31, 2019, 2018 or 2017. Valuation Assumptions Employee stock-based compensation expense was determined using the Black-Scholes option valuation model for stock options and employee share purchases under the ESPP. Option valuation models require the input of subjective assumptions and these assumptions can vary over time. The fair value of RSUs was based on the closing price of the underlying common stock on the date of grant. The Company bases its determination of expected volatility through its assessment of the historical volatility of its common stock. The Company relied on its historical exercise and post-vested termination activity for estimating its expected term for use in determining the fair value of these options. The weighted-average estimated fair value per share of options granted during 2019, 2018 and 2017 was $6.37, $11.39, and $4.10, respectively, based upon the assumptions used in the Black-Scholes valuation model. The assumptions used for estimating the fair value of the employee stock options were as follows: Year Ended December 31, 2019 2018 2017 Risk-free interest rate 1.68-2.25% 2.53-2.96% 1.81-2.28% Expected term (in years) 5.50-5.62 5.59-5.61 5.73-5.83 Expected dividend yield of stock — — — Expected volatility 76.46-78.39% 72.33-75.49% 71.11-72.30% Employees purchased 249,364, 328,710 and 253,994 shares of common stock through the ESPP at an average exercise price of $8.53, $4.51, and $3.22 per share during 2019, 2018 and 2017, respectively. The weighted-average estimated fair values of shares purchased under the Company’s ESPP during 2019, 2018 and 2017 were $4.70, $7.07 and $2.37, respectively, based upon the assumptions used in the Black-Scholes valuation model. The weighted–average assumptions used for estimating the fair value of the ESPP purchase rights are as follows: Year Ended December 31, 2019 2018 2017 Risk-free interest rate 1.53-2.42% 2.16-2.80% 0.44-0.76% Expected term (in years) 0.5 – 2.0 0.5-2.0 0.5-2.0 Expected dividend yield of stock — — — Expected volatility 51.02-91.96% 73.21-83.25% 66.39-82.19%

Employee Benefit Plan

Employee Benefit Plan	12 Months Ended
	Dec. 31, 2019
Retirement Benefits [Abstract]
Employee Benefit Plan	NOTE 10 – EMPLOYEE BENEFIT PLAN The Company sponsors a defined-contribution savings plan under Section 401(k) of the Internal Revenue Code covering all full-time employees (“Sangamo 401(k) Plan”). The Sangamo 401(k) Plan is intended to qualify under Section 401 of the Internal Revenue Code. The Company matched employee contributions equal to 50% for the first 8% in 2019, 2018 and 2017, up to a limit of $4,000 in 2019, 2018 and 2017. Matching funds are fully vested when contributed. Contributions to the Sangamo 401(k) Plan by the Company were $0.9 million, $0.8 million, and $0.5 million for the years ended December 31, 2019, 2018 and 2017, respectively.

Income Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2019
Income Tax Disclosure [Abstract]
Income Taxes	NOTE 11 – INCOME TAXES The domestic and foreign components of loss before income taxes were as follows (in thousands): Year Ended December 31, 2019 2018 2017 Domestic $ (77,354) $ (65,695) $ (54,568) Foreign (18,065) (3,194) — Loss before income taxes $ (95,419) $ (68,889) $ (54,568) The benefit for income taxes consisted of the following (in thousands): Year Ended December 31, 2019 2018 2017 Benefit for income taxes: Current: Federal $ — $ — $ — State — — — Foreign — — — Subtotal — — — Deferred: Federal — — — State — — — Foreign — — — Subtotal — — — Income tax benefit $ — $ — $ — The difference between the benefit for income taxes and the amount computed by applying the federal statutory income tax rate to loss before taxes is explained as follows (in thousands): Year Ended December 31, 2019 2018 2017 Tax at federal statutory rate (1) $ (20,038) $ (14,467) $ (18,553) State taxes, net (9,597) (2,849) 795 Federal rate change — — 53,045 Foreign rate differential (665) (177) — Non-deductible stock-based compensation 2,817 (2,729) 2,120 Research credits (3,429) (1,005) (869) Change in valuation allowance 29,655 20,271 (36,575) Other 1,257 956 37 Income tax benefit $ — $ — $ — ___________________ (1) For the year ended December 31, 2017 the statutory tax rate was 35%. For the years ended December 31, 2018 and 2019, as a result of Tax Reform, the statutory tax rate was decreased to 21%. Deferred income taxes reflect the net tax effects of temporary differences between the carrying amounts of assets and liabilities for financial reporting purposes and the amounts used for income tax purposes. Significant components of the Company’s deferred tax assets are as follows (in thousands): December 31, 2019 2018 Assets: Deferred tax assets: Net operating loss carryforwards $ 133,765 $ 138,896 Research and development tax credit carryforwards 21,459 16,829 Stock-based compensation 4,194 3,801 Deferred revenue 32,171 3,191 Fixed assets 11,282 — Lease liability 11,722 — Build to suit lease liability — 6,400 Accruals and reserves 675 — Other 151 604 Total deferred tax asset 215,419 169,721 Valuation allowance 187,724 158,150 Net deferred tax assets 27,695 11,571 Liabilities: Intangible assets (13,609) (14,100) Operating lease right-of-use assets (20,656) — Fixed assets — (4,176) Net deferred tax liability (34,265) (18,276) Total deferred tax liability $ (6,570) $ (6,705) In October 2018, the Company acquired Sangamo France. The Company recorded goodwill and intangible assets as part of accounting for the acquisition of Sangamo France. There is no corresponding tax basis for the goodwill or intangible assets. A portion of the intangible assets acquired were for the use in a particular research and development project IPR&D and are considered indefinite-lived assets with no tax basis. The changes in the fair value of the unrealized gain/loss on securities investment are recorded as a component of accumulated other comprehensive income, net of a provision for income taxes. A valuation allowance is recorded when it is more likely than not that all or some portion of the deferred income tax assets will not be realized. The Company regularly assesses the need for a valuation allowance against its deferred income tax assets by considering both positive and negative evidence related to whether it is more likely than not that the Company’s deferred income tax assets will be realized. In evaluating the Company’s ability to recover its deferred income tax assets within the jurisdiction from which they arise, the Company considers all available positive and negative evidence, including scheduled reversals of deferred income tax liabilities, projected future taxable income, tax-planning strategies, and results of recent operations. Accordingly, based upon the Company’s analysis of these factors the net deferred tax assets have been substantially offset by a valuation allowance. The valuation allowance (decreased) increased by $(29.6) million, $45.3 million and $(28.9) million for the years ended December 31, 2019, 2018 and 2017, respectively. As of December 31, 2019, Sangamo had net operating loss carryforwards for federal and state income tax purposes of approximately $489.4 million and $164.7 million, respectively. The federal net operating loss generated before 2018 will begin to expire in 2024 and will keep expiring through 2037, if not utilized. Federal net operating loss generated in 2018 will carry forward indefinitely. If not utilized, the state net operating loss carryforwards will begin to expire in 2029, respectively. The Company’s French net operating loss carryforward balance is $147.9 million, which carries over indefinitely. The Company also has federal and state research tax credit carryforwards of $16.4 million and $15.2 million, respectively. The federal research credits began to expire in 2018 while the state research credits have no expiration date. Utilization of the Company’s net operating loss carryforwards and research tax credit carryforwards may be subject to substantial annual limitations due to the ownership change limitations provided by the Internal Revenue Code and similar state provisions. The annual limitation could result in the expiration of the net operating loss carryforwards and research tax credit carryforwards before utilization. On December 22, 2017, the current administration signed the Tax Cuts and Jobs Act (“Tax Reform”) into legislation. The Tax Reform makes significant changes to the U.S. corporate income tax law including, but not limited to, (1) reducing the U.S. federal corporate tax rate to 35% from 21% and (2) requiring a one-time mandatory transition tax on previously deferred foreign earnings of U.S. subsidiaries. Under ASC Topic 740, the effects of changes in tax rates and laws are recognized in the period in which the new legislation is enacted. In the case of U.S. federal income taxes, the enactment date is the date the bill becomes law. On December 22, 2017, the SEC staff issued Staff Accounting Bulletin No. 118 (“SAB 118”), which provides guidance on accounting for the tax effects of the Tax Reform. SAB 118 provides a measurement period that should not extend beyond one year from the Tax Reform enactment date for companies to complete the accounting under ASC Topic 740 for the year ended December 31, 2018. In accordance with SAB 118, a company must reflect the income tax effects of those aspects of the Tax Reform for which the accounting under ASC Topic 740 is complete. The Company has finished their analysis as of the measurement period closing of December 22, 2018 after application of law changes were reviewed by the Company. There were no subsequent adjustments as the conclusions have remained the same. The Company’s policy is to reinvest the earnings of its non-U.S. subsidiaries in those operations. The Company does not provide for U.S. taxes on the earnings of foreign subsidiaries because the Company intends to reinvest such earnings offshore indefinitely. However, if these funds were repatriated, the Company would be required to accrue and pay applicable U.S. taxes and withholding taxes. Due to the losses generated in foreign countries there are no earnings to repatriate. The Company files federal and state income tax returns with varying statutes of limitations. The tax years from 2002 forward remain open to examination due to the carryover of net operating losses or tax credits. The Company also files United Kingdom and French income tax returns, and the tax years from 2008 and thereafter remain open in the United Kingdom and 2016 and thereafter in France are still subject to examination. The Company’s practice is to recognize interest and/or penalties related to income tax matters in income tax expense. As of December 31, 2019, the Company had no accrued interest and/or penalties. The unrecognized tax benefits may change during the next year for items that arise in the ordinary course of business. In the event that any unrecognized tax benefits are recognized, the effective tax rate will not be affected. The following table summarizes the activity related to the Company’s unrecognized tax benefits (in thousands): December 31, 2019 2018 2017 Beginning balance $ 6,288 $ 5,659 $ 5,045 Additions based on tax positions related to the current year 5,393 636 622 Additions for tax positions of prior years (51) (7) (8) Reductions for tax positions of prior years — — — Ending balance $ 11,630 $ 6,288 $ 5,659

Related Party Disclosures

Related Party Disclosures	12 Months Ended
	Dec. 31, 2019
Related Party Transactions [Abstract]
Related Party Transaction	RELATED PARTY TRANSACTIONDuring the year, the Company acquired 52,700 vested free shares from a former executive of Sangamo France who is now an executive of Sangamo, pursuant to the exercise of the Free Shares Options for approximately $0.1 million of cash.

Quarterly Financial Data (Unaud

Quarterly Financial Data (Unaudited)	12 Months Ended
	Dec. 31, 2019
Quarterly Financial Information Disclosure [Abstract]
Quarterly Financial Data (Unaudited)	NOTE 13 – QUARTERLY FINANCIAL DATA (UNAUDITED) The following table sets forth certain unaudited quarterly financial data for the eight quarters ended December 31, 2019. The unaudited information set forth below has been prepared on the same basis as the audited information contained herein and includes all adjustments necessary to present fairly the information set forth. The operating results for any quarter are not indicative of results for any future period. All amounts are in thousands except per share amounts. 2019 2018 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Revenues $ 8,071 $ 17,548 $ 21,958 $ 54,851 $ 12,637 $ 21,416 $ 23,562 $ 26,837 Operating expenses 51,968 51,052 51,206 53,382 33,634 40,556 39,803 47,609 Net (loss) income (42,203) (30,356) (27,361) 4,501 (20,187) (16,640) (12,843) (19,219) Net loss attributable to non-controlling interest (53) (72) (54) (54) — — — (555) Net (loss) income attributable to Sangamo Therapeutics, Inc. (42,150) (30,284) (27,307) 4,555 (20,187) (16,640) (12,843) (18,664) Basic and diluted net (loss) income per share attributable to Sangamo Therapeutics, Inc. (0.41) (0.26) (0.24) 0.04 (0.23) (0.17) (0.13) (0.18)

Subsequent Events

Subsequent Events	12 Months Ended
	Dec. 31, 2019
Subsequent Events [Abstract]
SUBSEQUENT EVENTS	SUBSEQUENT EVENTS In February 2020, the Company entered into a global licensing collaboration agreement with Biogen MA, Inc. and its affiliate, Biogen International GmbH, for the research, development and commercialization of gene regulation therapies for the treatment of neurological diseases. The companies plan to leverage the Company’s proprietary ZFP technology delivered via AAV to modulate expression of key genes involved in neurological diseases. Under the Biogen collaboration agreement, the Company will grant to Biogen an exclusive, royalty bearing and worldwide license, under its relevant patents and know-how, to develop, manufacture and commercialize certain ZFP and/or AAV-based products directed to up to 12 neurological disease gene targets selected by Biogen. Biogen has already selected three of these: ST-501 for tauopathies including Alzheimer’s disease, ST-502 for synucleinopathies including Parkinson’s disease, and a third undisclosed neuromuscular disease target. Biogen has exclusive rights to nominate up to nine additional targets over a target selection period of five years. For each gene target selected by Biogen, the Company will perform early research activities, costs for which will be shared by the companies, aimed at the development of the combination of proprietary CNS delivery vectors and ZFP-TFs (or potential other ZFP products) targeting therapeutically relevant genes. Biogen will then assume responsibility and costs for the IND-enabling studies, clinical development, related regulatory interactions, and global commercialization. The Company will be responsible for GMP manufacturing activities for the initial clinical trials for the first three products of the collaboration and plans to leverage its in-house manufacturing capacity. Biogen will assume responsibility for GMP manufacturing activities beyond the first clinical trial for each of the first three products. Subject to certain exceptions set forth in the Biogen collaboration agreement, the Company will be prohibited from developing, manufacturing or commercializing any therapeutic product directed to the targets selected by Biogen. After the Biogen collaboration agreement becomes effective, Biogen will pay the Company an upfront payment of $125.0 million. The Company is also eligible to receive research, development, regulatory and commercial milestone payments that could total up to approximately $2.37 billion if Biogen selects all of the targets allowed under the agreement and all the specified milestones set forth in the agreement are achieved, which includes up to $925.0 million in pre-approval milestone payments and up to $1,445.0 million in first commercial sale and other sales-based milestone payments. I n addition, the Company will also be eligible to receive tiered high single-digit to sub-teen royalties on potential net commercial sales of licensed products arising from the collaboration. These royalty payments will be subject to reduction due to patent expiration, entry of biosimilar products to the market and payments made under certain licenses for third-party intellectual property. The Biogen collaboration agreement will continue, on a product-by-product and country-by-country basis, until the expiration of the applicable royalty term. Biogen has the right to terminate the collaboration agreement, in its entirety or on target-by-target basis, for any reason after a specified notice period. Each party has the right to terminate this agreement on account of the other party’s bankruptcy or material, uncured breach. In addition, the Company may terminate the collaboration agreement if Biogen challenges any patents licensed by the Company to Biogen. Concurrently with the execution of the collaboration agreement, the Company also entered into a stock purchase agreement with Biogen MA, Inc., pursuant to which Biogen will purchase 24,420,157 shares of the Company’s common stock (the “Biogen Shares”), at a price per share of $9.2137, for an aggregate purchase price of $225.0 million. Pursuant to the terms of the stock purchase agreement, Biogen has agreed not to, without the Company’s prior written and subject to specified conditions and exceptions, directly or indirectly acquire shares of the Company’s outstanding common stock, seek or propose a tender or exchange offer or merger between the parties, solicit proxies or consents with respect to any matter, or undertake other specified actions related to the potential acquisition of additional equity interests in the Company. Such standstill restrictions expire on the earlier of the three The stock purchase agreement also provides that until the first anniversary of the effectiveness of the Biogen collaboration agreement, Biogen will hold and not sell any of the Biogen Shares and from the first anniversary through the second anniversary, Biogen will hold and not sell at least 50% of the Biogen Shares, in addition to being subject to certain volume limitations. The stock purchase agreement further provides that, subject to certain limitations, upon Biogen’s request, the Company will register for resale any of the Biogen Shares on a registration statement to be filed with the SEC, until such time as all remaining Biogen Shares may be sold pursuant to Rule 144 promulgated under the Securities Act during any 90-day period. In addition, Biogen has agreed that, excluding specified extraordinary matters, it will vote the Biogen Shares in accordance with the Company’s recommendation and has granted the Company an irrevocable proxy with respect to the foregoing. Such voting provisions expire on the earlier of (i) the two The consummation of the transactions under each of the Biogen collaboration agreement and the stock purchase agreement is subject to the satisfaction of customary closing conditions, including the expiration or termination of the applicable waiting period under the Hart-Scott-Rodino Antitrust Improvements Act of 1976, as amended.

Organization and Summary of S_2

Organization and Summary of Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2019
Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation The accompanying Consolidated Financial Statements have been prepared in conformity with generally accepted accounting principles in the United States of America (“U.S. GAAP”) and include the accounts of the Company and its subsidiaries. All intercompany balances and transactions have been eliminated in the Consolidated Financial Statements. For consolidated entities where we own or are exposed to less than 100% of the economics, we record net loss attributable to  non-controlling interests on our Consolidated Statements of Operations equal to the percentage of the economic or ownership interest retained in such entities by the respective noncontrolling parties.
Reclassifications	Reclassifications Certain prior period amounts in the accompanying Consolidated Financial Statements have been reclassified to conform to the current period presentation.
Use of Estimates	Use of EstimatesThe preparation of the accompanying Consolidated Financial Statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect the amounts reported in the financial statements and the accompanying notes. On an ongoing basis, management evaluates its estimates including critical accounting policies or estimates related to revenue recognition, clinical trial accruals, fair value of assets and liabilities, including from acquisitions, and stock-based compensation. Estimates are based on historical experience and on various other market specific and other relevant assumptions that the Company believes to be reasonable under the circumstances, the results of which form the basis for making judgments about the carrying values of assets and liabilities that are not readily apparent from other sources. Actual results could differ from those estimates. In March 2019, the Company recorded an adjustment to revenue related to a change in estimate in connection with the hemophilia A collaboration agreement with Pfizer Inc. (“Pfizer”). This adjustment was a direct result of the decision to increase the project scope during the first quarter of 2019 and the corresponding costs, both of which resulted in a decrease in the measure of proportional performance. In December 2019, the Company updated its estimated project cost and related revenues upon the transfer of the investigational new drug (“IND”) for Pfizer SB-525. This adjustment directly resulted in a decrease in project scope during the fourth quarter of 2019 and a decrease in the corresponding costs, which resulted in an increase in the measure of proportional performance.
Revenue Recognition	Revenue Recognition Effective January 1, 2018, the Company adopted the provisions of Accounting Standards Codification (“ASC”) Topic 606, Revenue from Contracts with Customers (“ASC Topic 606”) using the modified retrospective method, resulting in a change to its accounting policy for revenue recognition. ASC Topic 606 establishes a unified model to determine how revenue is recognized. The Company’s contract revenues are derived from collaboration agreements and research activity grants and licensing. Research and licensing agreements typically include upfront signing or license fees, cost reimbursements, research services, minimum sublicense fees, milestone payments and royalties on future licensee’s product sales. The Company has both fixed and variable consideration. Non-refundable upfront fees and funding of research and development activities are considered fixed, while milestone payments are generally identified as variable consideration. Sangamo’s research grants are typically multi-year agreements and provide for the reimbursement of qualified expenses for research and development as defined under the terms of the grant agreement. Revenues under research grant agreements are generally recognized when the related qualified research expenses are incurred. Deferred revenue represents the portion of research or license payments received but not earned. In determining the appropriate amount of revenue to be recognized as it fulfills its obligations under its agreements, the Company performs the following steps: (i) identification of the promised goods or services in the contract; (ii) determination of whether the promised goods or services are performance obligations, including whether they are distinct in the context of the contract; (iii) measurement of the transaction price, including the constraint on variable consideration; (iv) allocation of the transaction price to the performance obligations based on estimated selling prices; and (v) recognition of revenue when (or as) the Company satisfies each performance obligation. A performance obligation is a promise in a contract to transfer a distinct good or service to the customer and is the unit of account in ASC Topic 606. The Company’s performance obligations include license rights, development services and services associated with regulatory submission and approval processes. Revenues from research services earned under collaboration agreements are generally recognized as revenue as the related services are provided. Revenues from non-refundable upfront fees are recognized over time either by measuring progress towards satisfaction of the relevant performance obligation, using the input method (i.e. cumulative actual costs incurred relative to total estimated costs) or on a straight-line basis when a performance obligation is expected to be satisfied evenly over a period of time (or when the entity has a stand-ready obligation). Significant management judgment is required to determine the level of effort required under an arrangement, and the period over which the Company expects to complete its performance obligations under the arrangement which may include total internal personnel costs and external costs to be incurred as well as, in certain cases, the estimated stand-ready obligation period. Changes in these estimates can have a material effect on revenue recognized. If the Company cannot reasonably estimate when its performance obligations either are completed or become inconsequential, then revenue recognition is deferred until the Company can reasonably make such estimates. The Company includes the unconstrained amount of estimated variable consideration in the transaction price. The amount included in the transaction price is constrained to the amount for which it is probable that a significant reversal of cumulative revenue recognized will not occur. At the end of each subsequent reporting period, the Company re-evaluates the estimated variable consideration included in the transaction price and any related constraint and, if necessary, adjusts its estimate of the overall transaction price. Revenue is then recognized over the remaining estimated period of performance using the cumulative catch-up method. The estimated period of performance and project costs, such as personnel and manufacturing cost, are reviewed quarterly and adjusted, as needed, to reflect the Company’s current assumptions regarding the timing of its deliverables. As part of the accounting for these arrangements, the Company must develop assumptions that require judgment to determine the stand-alone selling price of each performance obligation identified in the contract. The Company uses key assumptions to determine the stand-alone selling price, which may include forecasted revenues, development timelines, reimbursement rates for personnel costs, discount rates and probabilities of technical and regulatory success. Related costs and expenses under these arrangements have historically approximated the revenues recognized. Receivables from collaborations are typically unsecured and are concentrated in the biopharmaceutical industry. Accordingly, the Company may be exposed to credit risk generally associated with biopharmaceutical companies or specific to its collaboration agreements. To date, the Company has not experienced any losses related to these receivables. Funds received from third parties under contract or funds received from grant arrangements are generally recorded as revenue if the Company is deemed to be the principal participant in the arrangements because the activities under the contracts or grants are part of the Company’s development programs. Contract funds received are not refundable and are recognized when the related qualified research and development costs are incurred and there is reasonable assurance that the funds will be received. Funds received in advance are recorded as deferred revenue.
Business Combinations	Business Combinations The Company accounts for acquisitions using the acquisition method of accounting, which requires that assets acquired, including in-process research and development (“IPR&D”) projects, liabilities assumed and any non-controlling interests in the acquired target in an acquisition be recorded at their fair values as of the acquisition date on the Company’s Consolidated Balance Sheets. Any excess of purchase price over the fair value of net assets acquired is recorded as goodwill. The determination of estimated fair value requires the Company to make significant estimates and assumptions. As a result, the Company may record adjustments to the fair values of assets acquired and liabilities assumed within the measurement period (up to one year from the acquisition date) with the corresponding offset to goodwill. Transaction costs associated with business combinations are expensed as they are incurred.
Goodwill and Intangible Assets	Goodwill and Intangible Assets Goodwill represents the excess of the consideration transferred over the estimated fair values of assets acquired and liabilities assumed in a business combination. Intangible assets with indefinite useful lives are related to purchased IPR&D projects and are measured at their respective fair values as of the acquisition date. Goodwill and intangible assets with indefinite useful lives are not amortized. Intangible assets related to IPR&D projects are considered to be indefinite-lived until the completion or abandonment of the associated research and development efforts. If and when development is complete, which generally occurs if and when regulatory approval to market a product is obtained, the associated assets would be deemed finite-lived and would then be amortized based on their respective estimated useful lives at that point in time. The Company tests goodwill and indefinite-lived intangible assets for impairment on an annual basis and between annual tests if the Company becomes aware of any events occurring or changes in circumstances that would indicate the fair values of the assets are below their respective carrying amounts. As of December 31, 2019, no impairment of goodwill or indefinite-lived intangible assets has been identified.
Valuation of Long-Lived Assets	Valuation of Long-Lived Assets Long-lived assets, including property and equipment and finite-lived intangible assets, are reviewed for impairment whenever facts or circumstances either internally or externally may suggest that the carrying value of an asset may not be recoverable. Recoverability of these assets is measured by comparison of the carrying amount of each asset to the future undiscounted cash flows expected to result from the use of the asset and its eventual disposition. If the asset is considered to be impaired, the amount of any impairment is measured as the difference between the carrying value and the fair value of the impaired asset. As of December 31, 2019, no impairment of any long-lived assets has been identified.
Fair Value Measurements	Fair Value Measurements The carrying amounts for financial instruments consisting of cash and cash equivalents, accounts receivable, accounts payable and accrued liabilities approximate fair value due to their short maturities. Marketable securities are stated at their estimated fair values. The free share asset/liability is measured using a binomial-lattice pricing model and is reviewed each reporting period and adjusted, as needed, and is expected to approximate fair value.
Cash, Cash Equivalents and Restricted Cash	Cash, Cash Equivalents and Restricted Cash Sangamo considers all highly-liquid investments purchased with original maturities of three months or less at the purchase date to be cash equivalents. Cash and cash equivalents consist of cash, deposits in demand money market accounts, and commercial paper.
Marketable Securities	Marketable Securities Sangamo classifies its marketable securities as available-for-sale and records its investments at estimated fair value based on quoted market prices or observable market inputs of almost identical assets, with the unrealized holding gains and losses included in accumulated other comprehensive loss (“AOCI”). The Company classifies those investments that are not required for use in current operations and that mature in more than 12 months as non-current marketable securities in the accompanying Consolidated Balance Sheets. The Company’s investments are subject to a periodic impairment review. The Company recognizes an impairment charge, if material, when a decline in the fair value of its investments below the cost basis is judged to be other-than-temporary. The Company considers various factors in determining whether to recognize an impairment charge, including the length of time and extent to which the fair value has been less than the Company’s cost basis, the financial condition and near-term prospects of the investee and the Company’s intent and ability to hold the investment for a period of time sufficient to allow for any anticipated recovery in the market value. Realized gains and losses on available-for-sale securities are included in other income, net, which are determined using the specific identification method.
Property and Equipment	Property and Equipment Property and equipment are stated at cost, less accumulated depreciation and amortization. Depreciation is calculated using the straight-line method based on the estimated useful lives of the related assets which is generally three
Research and Development Expenses	Research and Development Expenses Research and development expenses consist primarily of personnel costs, including salaries, benefits and stock-based compensation, clinical studies performed by contract research organizations ("CROs"), materials and supplies and overhead allocations consisting of various support and facility-related costs. Research and development costs are expensed as incurred.
General and Administrative Expenses	General and Administrative Expenses General and administrative expenses consist of finance, human resources, legal and other administrative activities. These expenses consist primarily of personnel costs, including salaries, benefits and stock-based compensation, facilities and overhead costs, legal expenses, and other general and administrative costs.
Stock-based Compensation	Stock-based Compensation The Company measures and recognizes compensation expense for all stock-based payment awards made to Sangamo employees and directors, including employee share options, restricted stock units (“RSUs”) and employee stock purchases related to the 2010 Employee Stock Purchase Plan (“ESPP”), as amended, based on estimated fair values at the award grant date. The fair value of stock-based awards is amortized over the vesting period of the award using a straight-line method. To estimate the fair value of an award, the Company uses the Black-Scholes option pricing model. This model requires inputs such as expected life, expected volatility and risk-free interest rate. These inputs are subjective and generally require significant analysis and judgment to develop. While estimates of expected life and volatility are derived primarily from the Company’s historical data, the risk-free rate is based on the U.S. Treasury yield curve in effect at the time of grant commensurate with the expected life assumption. The Company accounts for forfeitures in the period they occur.
Income Taxes	Income Taxes Income tax expense has been provided using the liability method. Deferred tax assets and liabilities are determined based on the difference between the financial statement and tax bases of assets and liabilities as measured by the enacted tax rates that will be in effect when these differences reverse. The Company provides a valuation allowance against net deferred tax assets if, based upon the available evidence, it is not more likely than not that the deferred tax assets will be realized. The Company recognizes a tax benefit from an uncertain tax position only if it is more likely than not that the tax position will be sustained on examination by the taxing authorities, based on the technical merits of the position. The tax benefits recognized in the Company’s consolidated financial statements from such positions are measured based on the largest benefit that has a greater than 50% likelihood of being realized. The Company recognizes interest and penalties associated with tax matters as part of the income tax provision and includes accrued interest and penalties with the related income tax liability within account payable and accrued liabilities on its Consolidated Balance Sheets.
Foreign Currency Translation	Foreign Currency Translation The functional currency of the Company’s foreign subsidiaries is primarily the Euro. Assets and liabilities denominated in foreign currencies are translated to U.S. dollars using the exchange rates at the balance sheet date. Foreign currency translation adjustments are recorded as a component of AOCI within stockholders’ equity. Revenues and expenses from the Company’s foreign subsidiaries are translated using the monthly average exchange rates in effect during the period in which the transactions occur. Foreign currency transaction gains and losses are recorded in interest and other income, net, on the Company’s Consolidated Statements of Operations.
Net Loss Per Share	Net Loss Per Share Basic net loss per share attributable to Sangamo Therapeutics, Inc. stockholders has been computed by dividing net loss attributable to Sangamo Therapeutics, Inc. stockholders by the weighted-average number of shares of common stock outstanding during the period. Diluted net loss per share attributable to Sangamo Therapeutics, Inc. stockholders is calculated by dividing net loss attributable to Sangamo Therapeutics, Inc. stockholders by the weighted-average number of shares of common stock plus potential dilutive securities outstanding during the period.
Segments	SegmentsThe Company operates in one segment. Management uses one measure of profitability and does not segregate its business for internal reporting.
Recent Accounting Pronouncements	Recent Accounting Pronouncements Recently Adopted Simplified Disclosure In August 2018, the Securities and Exchange Commission ("SEC") adopted amendments to certain disclosure requirements in Securities Act Release No. 33-10532, Disclosure Update and Simplification , as updated. These amendments eliminate, modify, or integrate into other SEC requirements certain disclosure rules. Among the amendments is the requirement to present an analysis of changes in stockholders’ equity in the interim financial statements included in quarterly reports on Form 10-Q. The analysis, which can be presented as a footnote or separate statement, is required for the current and comparative quarter and year-to-date interim periods. The amendments are effective for all filings made on or after November 5, 2018. The Company’s adoption of these SEC amendments had no material effect on the Company’s reporting of financial position, results of operations, cash flows or stockholders’ equity. Accounting for Leases In February 2016, the Financial Accounting Standards Board (“FASB”) issued ASU 2016-2, Leases (“ASC Topic 842”). ASC Topic 842 amends a number of aspects of lease accounting, including requiring lessees to recognize almost all leases with a term greater than one year as a right-of-use (“ROU”) asset and corresponding liability, measured at the present value of the lease payments. On January 1, 2019, the Company adopted ASC Topic 842 using the modified retrospective approach with a cumulative-effect adjustment of $0.9 million reflected as a decrease to the opening balance of accumulated deficit as of the adoption date. Results for the year ended December 31, 2019 are presented under ASC Topic 842. No prior period amounts were adjusted and continue to be reported in accordance with previous lease guidance, ASC Topic 840 – Leases (“ASC Topic 840”). ASC Topic 842 provides a number of optional practical expedients in transition. The Company elected the practical expedients to not reassess its prior conclusions about lease identification under the new standard, to not reassess lease classification, and to not reassess initial direct costs. The Company did not elect the practical expedient allowing the use-of-hindsight, which would require the Company to reassess the lease term of its leases based on all facts and circumstances through the effective date. The Company also did not elect the practical expedient pertaining to land easements, as this is not applicable to the current contract portfolio. The impact of the adoption of ASC Topic 842 on the accompanying Consolidated Balance Sheet as of January 1, 2019 was as follows (in thousands): December 31, 2018 Adjustments Due to the Adoption of ASC Topic 842 January 1, 2019 Assets: Property and equipment, net $ 78,723 $ (62,500) $ 16,223 Operating lease right-of-use assets — 8,753 8,753 Prepaid rent — 36,025 36,025 Liabilities: Operating lease liabilities - current (1) — 1,408 1,408 Deferred rent (1) 271 (271) — Build-to-suit lease obligation (2) 27,689 (27,689) — Operating lease liabilities - long-term (2) — 7,933 7,933 Accumulated deficit (562,696) 897 (561,799) ___________________ (1) Operating lease liabilities – current and deferred rent are included in accounts payable and accrued liabilities on the Consolidated Balance Sheets. (2) Build-to-suit lease obligation and operating lease liabilities – long-term are included in long-term portion of lease liabilities on the Consolidated Balance Sheets. The adjustments due to the adoption of ASC Topic 842 primarily related to the recognition of operating lease ROU assets and operating lease liabilities for the Company’s leases. In addition, the adoption of ASC Topic 842 resulted in a change in accounting of the build-to-suit component of two leases under ASC Topic 840 to operating leases under ASC Topic 842. As a result, the Company derecognized the estimated fair value of the building shells that were included in Property and equipment, net as of December 31, 2018, as the Company had been deemed to own these buildings under ASC Topic 840. For a description of the leases, see “Note 7 – Commitments and Contingencies – Leases ” in these Consolidated Financial Statements. Not Yet Adopted Collaborative Arrangements In November 2018, the FASB issued ASU 2018-18, Collaborative Arrangements (ASC Topic 808): Clarifying the Interaction between Topic 808 and Topic 606 (“ASC Topic 808”), which clarifies that certain transactions between participants in a collaborative arrangement should be accounted for under ASC Topic 606 when the counterparty is a customer. In addition, ASC Topic 808 precludes an entity from presenting consideration from a transaction in a collaborative arrangement as revenue from contracts with customers if the counterparty is not a customer for that transaction. This guidance will be effective for the Company beginning January 1, 2020. The Company has determined the adoption of ASU 2018-18 will not have a material impact on its Consolidated Financial Statements. Goodwill Impairment Testing In January 2017, the FASB issued ASU No. 2017-4, Intangibles – Goodwill and Other (Topic 350): Simplifying the Test of Goodwill Impairment (“ASU 2017-4”). The new guidance simplifies the subsequent measurement of goodwill by eliminating Step 2 from the goodwill impairment test. ASU 2017-4 requires goodwill impairment to be measured as the amount by which a reporting unit’s carrying amount exceeds its fair value, not to exceed the carrying amount of its goodwill. ASU 2017-4 requires prospective application and is effective for annual periods beginning after December 15, 2019. ASU 2017-4 will require the Company to amend its methodology for determining any goodwill impairment beginning in 2020. The Company does not expect the adoption of ASU 2017-4 to have a material impact on its Consolidated Financial Statements. Credit Losses In June 2016, the FASB issued ASU No. 2016-13, Financial Instruments – Credit Losses (Topic 326) ("ASU 2016-13"). ASU 2016-13 implements an impairment model, known as the current expected credit loss model that is based on expected losses rather than incurred losses. Under the new guidance, an entity will recognize as an allowance its estimate of expected credit losses. ASU 2016-13 is effective for all interim and annual reporting periods beginning after December 15, 2019 and must be adopted using a modified retrospective approach, with certain exceptions. Early adoption is permitted. The Company does not expect the adoption of ASU 2016-13 to have a material impact on its Consolidated Financial Statements. Income Taxes In December 2019, the FASB issued ASU No. 2019-12, Income Taxes – Simplifying the Accounting for Income Taxes (“ASU 2019-12”). The guidance removes exceptions to the general principles in Income Taxes (Topic 740) for allocating tax expense between financial statement components, accounting basis differences stemming from an ownership change in foreign investments and interim period income tax accounting for year-to-date losses that exceed projected losses. The guidance becomes effective for annual reporting periods beginning after December 15, 2020 and interim periods within those fiscal years with early adoption permitted. The Company plans to adopt ASU 2019-12 effective January 1, 2020 and does not expect this adoption to have a material impact on its Consolidated Financial Statements.

Organization and Summary of S_3

Organization and Summary of Significant Accounting Policies (Tables)	12 Months Ended
	Dec. 31, 2019
Accounting Policies [Abstract]
Schedule of Revenue from Strategic Partnering Collaboration Agreements and Research Activity Grants as a Percentage of Total Revenues	Revenues from collaboration agreements and research activity grants as a percentage of total revenues were as follows: Year Ended December 31, 2019 2018 2017 Pfizer Inc. 40 % 47 % 47 % Kite Pharma, Inc. 34 % 30 % — Sanofi Genzyme 22 % 16 % 34 %
Schedule of Cash and Cash Equivalents	A reconciliation of cash, cash equivalents and restricted cash reported within the Consolidated Balance Sheets to the amounts reported within the accompanying Consolidated Statements of Cash Flows is as follows (in thousands): As of December 31, 2019 2018 2017 Cash and cash equivalents $ 80,428 $ 140,418 $ 49,826 Non-current restricted cash 1,500 3,500 3,500 Cash, cash equivalents and restricted cash as reported within the Consolidated Statements of Cash Flows $ 81,928 $ 143,918 $ 53,326
Restrictions on Cash and Cash Equivalents	A reconciliation of cash, cash equivalents and restricted cash reported within the Consolidated Balance Sheets to the amounts reported within the accompanying Consolidated Statements of Cash Flows is as follows (in thousands): As of December 31, 2019 2018 2017 Cash and cash equivalents $ 80,428 $ 140,418 $ 49,826 Non-current restricted cash 1,500 3,500 3,500 Cash, cash equivalents and restricted cash as reported within the Consolidated Statements of Cash Flows $ 81,928 $ 143,918 $ 53,326
Schedule of New Accounting Pronouncements and Changes in Accounting Principles	The impact of the adoption of ASC Topic 842 on the accompanying Consolidated Balance Sheet as of January 1, 2019 was as follows (in thousands): December 31, 2018 Adjustments Due to the Adoption of ASC Topic 842 January 1, 2019 Assets: Property and equipment, net $ 78,723 $ (62,500) $ 16,223 Operating lease right-of-use assets — 8,753 8,753 Prepaid rent — 36,025 36,025 Liabilities: Operating lease liabilities - current (1) — 1,408 1,408 Deferred rent (1) 271 (271) — Build-to-suit lease obligation (2) 27,689 (27,689) — Operating lease liabilities - long-term (2) — 7,933 7,933 Accumulated deficit (562,696) 897 (561,799) ___________________ (1) Operating lease liabilities – current and deferred rent are included in accounts payable and accrued liabilities on the Consolidated Balance Sheets. (2) Build-to-suit lease obligation and operating lease liabilities – long-term are included in long-term portion of lease liabilities on the Consolidated Balance Sheets.

Fair Value Measurement (Tables)

Fair Value Measurement (Tables)	12 Months Ended
	Dec. 31, 2019
Fair Value Disclosures [Abstract]
Summary of Fair Value Measurements of Cash Equivalents, Available-for-Sale Securities and Free Share Liability	The fair value measurements of the Company’s cash equivalents, available-for-sale securities and the free share asset/liability are identified at the following levels within the fair value hierarchy (in thousands): December 31, 2019 Fair Value Measurement Total Level 1 Level 2 Level 3 Assets: Cash equivalents: Money market funds $ 30,496 $ 30,496 $ — $ — Commercial paper securities 2,999 — 2,999 — Total 33,495 30,496 2,999 — Marketable securities: Commercial paper securities 155,368 — 155,368 — Corporate debt securities 95,017 — 95,017 — U.S. government-sponsored entity debt securities 53,493 — 53,493 — Total 303,878 — 303,878 — Total cash equivalents and marketable securities $ 337,373 $ 30,496 $ 306,877 $ — Free shares asset $ 236 $ — $ — $ 236 December 31, 2018 Fair Value Measurement Total Level 1 Level 2 Level 3 Assets: Cash equivalents: Money market funds $ 103,291 $ 103,291 $ — $ — Total 103,291 103,291 — — Marketable securities: Commercial paper securities 177,224 — 177,224 — Corporate debt securities 63,870 — 63,870 — U.S. government-sponsored entity debt securities 18,621 — 18,621 — Total 259,715 — 259,715 — Total cash equivalents and marketable securities $ 363,006 $ 103,291 $ 259,715 $ — Liabilities: Free shares liability $ 154 $ — $ — $ 154
Summary of Estimated Fair Value of Free Share Liability Assumptions	December 31, Free Shares valuation assumptions: 2019 2018 Sangamo Stock Price (USD) $ 8.68 $ 11.48 Sangamo France Stock Price (EUR) € 2.14 € 2.58 USD/ EUR Exchange Rate 0.91 0.87 Estimated Correlation Sangamo and Sangamo France Stock Prices 100.0 % — Sangamo Stock Price (USD) Volatility Estimate 72.5 % 79.9 % Sangamo France Stock Price (EUR) Volatility Estimate 72.5 % 8.6 % USD/ EUR Exchange Rate Volatility Estimate 6.6 % 7.7 % Risk Free Rate and Cost of Debt by Expected Exercise Date Varies Varies

Marketable Securities (Tables)

Marketable Securities (Tables)	12 Months Ended
	Dec. 31, 2019
Investments, Debt and Equity Securities [Abstract]
Summary of Cash Equivalents and Available-for-Sale Securities	The table below summarizes the Company’s cash equivalents and available-for-sale securities (in thousands): Amortized Gross Gross Estimated December 31, 2019 Cash equivalents: Money market funds $ 30,496 $ — $ — $ 30,496 Commercial paper securities 2,998 1 — 2,999 Total 33,494 1 — 33,495 Available-for-sale securities: Commercial paper securities 155,230 145 (7) 155,368 Corporate debt securities 94,905 115 (3) 95,017 U.S. government-sponsored entity debt securities 53,411 91 (9) 53,493 Total 303,546 351 (19) 303,878 Total cash equivalents and available-for-sale securities $ 337,040 $ 352 $ (19) $ 337,373 December 31, 2018 Cash equivalents: Money market funds $ 103,291 $ — $ — $ 103,291 Total 103,291 — — 103,291 Available-for-sale securities: Commercial paper securities 177,353 — (129) 177,224 Corporate debt securities 63,981 — (111) 63,870 U.S. government-sponsored entity debt securities 18,640 — (19) 18,621 Total 259,974 — (259) 259,715 Total cash equivalents and available-for-sale securities $ 363,265 $ — $ (259) $ 363,006 The fair value of investments available-for-sale by contractual maturity were as follows (in thousands): December 31, 2019 2018 Maturing in one year or less $ 282,046 $ 259,715 Maturing after one year through five years 21,832 — Total investments available-for-sale $ 303,878 $ 259,715

Major Customers, Partnerships_2

Major Customers, Partnerships and Strategic Alliances (Tables)	12 Months Ended
	Dec. 31, 2019
Kite Pharma, Inc. ("Kite")
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Revenues recognized under agreement	Revenues recognized under the agreement were as follows (in thousands): Year Ended December 31, 2019 2018 Revenue related to Kite agreement: Recognition of license and stand-ready fee $ 24,977 $ 18,545 Research services 9,373 6,972 Total $ 34,350 $ 25,517
Pfizer SB-525
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Revenues recognized under agreement	Revenues recognized under the agreement were as follows (in thousands): Year Ended December 31, 2019 2018 2017 Revenue related to Pfizer SB-525 agreement: Recognition of upfront fee and research services $ 15,697 $ 37,810 $ 17,008 Milestone achievement 23,662 — — Total $ 39,359 $ 37,810 $ 17,008
Pfizer C9ORF72
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Revenues recognized under agreement	Revenues recognized under the agreement were as follows (in thousands): Year Ended December 31, 2019 2018 2017 Recognition of upfront fee related to Pfizer C9ORF72 agreement $ 1,827 $ 2,188 $ —
Sanofi
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Revenues recognized under agreement	Revenues recognized under the agreement were as follows (in thousands): Year Ended December 31, 2019 2018 2017 Revenue related to Sanofi agreement: Recognition of upfront fee $ 3,494 $ 4,013 $ 1,769 Research services 6,367 9,503 10,489 Milestone achievement 12,819 — — Total $ 22,680 $ 13,516 $ 12,258

Acquisition of Acquisition of S

Acquisition of Acquisition of Sangamo France (Tables)	12 Months Ended
	Dec. 31, 2019
Business Combinations [Abstract]
Summary of Estimated Fair Value of Net Assets Acquired	The following table summarizes the estimated consideration transferred and the fair value of the net assets acquired as of the Acquisition Date (in thousands): October 1, 2018 Consideration transferred $ 45,911 Fair value of non-controlling interest 35,829 Fair value of Sangamo France $ 81,740 Cash $ 4,779 Current assets 2,427 Property and equipment 1,857 IPR&D 55,019 Other assets 155 Current liabilities (9,761) Assumed debt liabilities (4,933) Deferred tax liability, net (6,798) Fair value of net identifiable assets acquired 42,745 Goodwill 38,995 Total fair value of net assets acquired $ 81,740
Summary of Non-controlling Interest	Non-controlling interest as of December 31, 2019 was as follows (in thousands): Total Balance, beginning of year $ 739 Fair value of additional shares acquired (321) Loss attributable to non-controlling interest (233) Balance, end of year $ 185

Other Balance Sheet Details (Ta

Other Balance Sheet Details (Tables)	12 Months Ended
	Dec. 31, 2019
Balance Sheet Related Disclosures [Abstract]
Summary of Property and Equipment, Net	Property and equipment, net consist of the following (in thousands): December 31, 2019 2018 Laboratory equipment $ 17,179 $ 11,466 Furniture and fixtures 4,639 3,840 Leasehold improvements 13,888 3,640 Buildings — 3,876 Construction in progress 5,901 65,211 41,607 88,033 Less: accumulated depreciation and amortization (11,681) (9,310) Property and equipment, net $ 29,926 $ 78,723
Schedule of Intangible Assets and Goodwill	The changes in intangible assets were as follows (in thousands): December 31, 2019 2018 Balance, beginning of year $ 54,243 $ — Indefinite-lived assets - IPR&D — 55,019 Foreign currency translation adjustment (1,087) (776) Balance, end of year $ 53,156 $ 54,243 The changes in goodwill were as follows (in thousands): December 31, 2019 2018 Balance, beginning of year $ 40,044 $ 1,585 Goodwill acquired — 38,995 Foreign currency translation adjustment (771) (536) Balance, end of year $ 39,273 $ 40,044
Summary of Accounts Payable and Accrued Liabilities	Accounts payable and accrued liabilities consist of the following (in thousands): December 31, 2019 2018 Accounts payable $ 6,671 $ 3,355 Accrued research and development expenses 4,102 10,999 Operating lease liabilities - current 3,214 — Accrued professional fees 1,118 1,930 Deferred rent — 204 Other 2,451 4,969 Total accounts payable and accrued liabilities $ 17,556 $ 21,457

Commitments and Contingencies (

Commitments and Contingencies (Tables)	12 Months Ended
	Dec. 31, 2019
Commitments and Contingencies Disclosure [Abstract]
Summary of Future Minimum Payments under Contractual Obligations	Future minimum payments under lease obligations at December 31, 2019 consist of the following (in thousands): Total 2020 $ 5,870 2021 6,390 2022 6,468 2023 6,556 2024 6,694 Thereafter 26,141 Total lease payments 58,119 Less: Imputed interest (13,713) Total $ 44,406 Reported as of December 31, 2019: Operating lease liabilities - current (included in Accounts payable and accrued liabilities on the Consolidated Balance Sheet) $ 3,214 Operating lease liabilities - long-term 41,192 Total $ 44,406

Stockholders' Equity (Tables)

Stockholders' Equity (Tables)	12 Months Ended
	Dec. 31, 2019
Equity [Abstract]
Summary of Stock Option Activity	A summary of Sangamo’s stock option activity is as follows: Number of Weighted- Weighted-Average Aggregate (In years) (In thousands) Options outstanding at December 31, 2018 8,726,092 $ 11.23 Options granted 4,530,288 $ 9.68 Options exercised (806,226) $ 5.08 Options canceled (2,620,867) $ 12.39 Options outstanding at December 31, 2019 9,829,287 $ 10.71 7.91 $ 7,472 Options vested and expected to vest at December 31, 2019 9,829,287 $ 10.71 7.91 $ 7,472 Options exercisable at December 31, 2019 3,993,645 $ 10.43 6.54 $ 5,442
Summary of Restricted Stock Unit Activity	A summary of Sangamo’s RSU activity is as follows: Number of Weighted-Average Aggregate Intrinsic (In years) (In thousands) RSUs outstanding at December 31, 2018 322,701 RSUs awarded 834,745 RSUs released (118,807) RSUs forfeited (175,789) RSUs outstanding at December 31, 2019 862,850 1.22 $ 7,222 RSUs vested and expected to vest at December 31, 2019 862,850 1.22 $ 7,222

Stock-Based Compensation (Table

Stock-Based Compensation (Tables)	12 Months Ended
	Dec. 31, 2019
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Stock-Based Compensation Expense	The following table shows total stock-based compensation expense recognized in the accompanying Consolidated Statements of Operations (in thousands): Year Ended December 31, 2019 2018 2017 Research and development $ 10,135 $ 8,249 $ 5,031 General and administrative 9,195 6,428 4,058 Total stock-based compensation expense $ 19,330 $ 14,677 $ 9,089
Assumptions Used for Estimating Fair Value of Employee Stock Options	The assumptions used for estimating the fair value of the employee stock options were as follows: Year Ended December 31, 2019 2018 2017 Risk-free interest rate 1.68-2.25% 2.53-2.96% 1.81-2.28% Expected term (in years) 5.50-5.62 5.59-5.61 5.73-5.83 Expected dividend yield of stock — — — Expected volatility 76.46-78.39% 72.33-75.49% 71.11-72.30%
Weighted-Average Assumptions Used for Estimating Fair Value of ESPP Purchase Rights	The weighted–average assumptions used for estimating the fair value of the ESPP purchase rights are as follows: Year Ended December 31, 2019 2018 2017 Risk-free interest rate 1.53-2.42% 2.16-2.80% 0.44-0.76% Expected term (in years) 0.5 – 2.0 0.5-2.0 0.5-2.0 Expected dividend yield of stock — — — Expected volatility 51.02-91.96% 73.21-83.25% 66.39-82.19%

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2019
Income Tax Disclosure [Abstract]
Summary of Domestic and Foreign Components of Loss Before Income Taxes	The domestic and foreign components of loss before income taxes were as follows (in thousands): Year Ended December 31, 2019 2018 2017 Domestic $ (77,354) $ (65,695) $ (54,568) Foreign (18,065) (3,194) — Loss before income taxes $ (95,419) $ (68,889) $ (54,568)
Summary of Benefit for Income Taxes	The benefit for income taxes consisted of the following (in thousands): Year Ended December 31, 2019 2018 2017 Benefit for income taxes: Current: Federal $ — $ — $ — State — — — Foreign — — — Subtotal — — — Deferred: Federal — — — State — — — Foreign — — — Subtotal — — — Income tax benefit $ — $ — $ —
Schedule of Difference Between Benefit for Income Taxes and Federal Statutory Income Tax Rate	The difference between the benefit for income taxes and the amount computed by applying the federal statutory income tax rate to loss before taxes is explained as follows (in thousands): Year Ended December 31, 2019 2018 2017 Tax at federal statutory rate (1) $ (20,038) $ (14,467) $ (18,553) State taxes, net (9,597) (2,849) 795 Federal rate change — — 53,045 Foreign rate differential (665) (177) — Non-deductible stock-based compensation 2,817 (2,729) 2,120 Research credits (3,429) (1,005) (869) Change in valuation allowance 29,655 20,271 (36,575) Other 1,257 956 37 Income tax benefit $ — $ — $ — ___________________ (1) For the year ended December 31, 2017 the statutory tax rate was 35%. For the years ended December 31, 2018 and 2019, as a result of Tax Reform, the statutory tax rate was decreased to 21%.
Schedule of Company's Deferred Tax Assets	Significant components of the Company’s deferred tax assets are as follows (in thousands): December 31, 2019 2018 Assets: Deferred tax assets: Net operating loss carryforwards $ 133,765 $ 138,896 Research and development tax credit carryforwards 21,459 16,829 Stock-based compensation 4,194 3,801 Deferred revenue 32,171 3,191 Fixed assets 11,282 — Lease liability 11,722 — Build to suit lease liability — 6,400 Accruals and reserves 675 — Other 151 604 Total deferred tax asset 215,419 169,721 Valuation allowance 187,724 158,150 Net deferred tax assets 27,695 11,571 Liabilities: Intangible assets (13,609) (14,100) Operating lease right-of-use assets (20,656) — Fixed assets — (4,176) Net deferred tax liability (34,265) (18,276) Total deferred tax liability $ (6,570) $ (6,705)
Summary of Activity Related to Company's Unrecognized Tax Benefits	The following table summarizes the activity related to the Company’s unrecognized tax benefits (in thousands): December 31, 2019 2018 2017 Beginning balance $ 6,288 $ 5,659 $ 5,045 Additions based on tax positions related to the current year 5,393 636 622 Additions for tax positions of prior years (51) (7) (8) Reductions for tax positions of prior years — — — Ending balance $ 11,630 $ 6,288 $ 5,659

Quarterly Financial Data (Una_2

Quarterly Financial Data (Unaudited) (Tables)	12 Months Ended
	Dec. 31, 2019
Quarterly Financial Information Disclosure [Abstract]
Summary of Quarterly Financial Data	The following table sets forth certain unaudited quarterly financial data for the eight quarters ended December 31, 2019. The unaudited information set forth below has been prepared on the same basis as the audited information contained herein and includes all adjustments necessary to present fairly the information set forth. The operating results for any quarter are not indicative of results for any future period. All amounts are in thousands except per share amounts. 2019 2018 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Revenues $ 8,071 $ 17,548 $ 21,958 $ 54,851 $ 12,637 $ 21,416 $ 23,562 $ 26,837 Operating expenses 51,968 51,052 51,206 53,382 33,634 40,556 39,803 47,609 Net (loss) income (42,203) (30,356) (27,361) 4,501 (20,187) (16,640) (12,843) (19,219) Net loss attributable to non-controlling interest (53) (72) (54) (54) — — — (555) Net (loss) income attributable to Sangamo Therapeutics, Inc. (42,150) (30,284) (27,307) 4,555 (20,187) (16,640) (12,843) (18,664) Basic and diluted net (loss) income per share attributable to Sangamo Therapeutics, Inc. (0.41) (0.26) (0.24) 0.04 (0.23) (0.17) (0.13) (0.18)

Organization and Summary of S_4

Organization and Summary of Significant Accounting Policies - Additional Information (Detail) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019USD ($)shares	Sep. 30, 2019USD ($)	Jun. 30, 2019USD ($)	Mar. 31, 2019USD ($)	Dec. 31, 2018USD ($)shares	Sep. 30, 2018USD ($)	Jun. 30, 2018USD ($)	Mar. 31, 2018USD ($)	Dec. 31, 2019USD ($)segment$ / sharesshares	Dec. 31, 2018USD ($)shares	Dec. 31, 2017USD ($)shares	Jan. 01, 2019USD ($)	Jan. 01, 2018USD ($)
Organization and Summary of Significant Accounting Policies [Line Items]
Revenues	$ 54,851	$ 21,958	$ 17,548	$ 8,071	$ 26,837	$ 23,562	$ 21,416	$ 12,637	$ 102,428	$ 84,452	$ 36,567
Net loss	4,501	$ (27,361)	$ (30,356)	$ (42,203)	$ (19,219)	$ (12,843)	$ (16,640)	$ (20,187)	(95,419)	$ (68,889)	$ (54,568)
Letter of credit	$ 1,500								$ 1,500
Stock options and RSUs outstanding (in shares) | shares	10,750,550				9,048,793				10,750,550	9,048,793	8,367,628
Number of operating segments | segment									1
Cumulative effect of new accounting principle in period of adoption												$ (897)	$ (1,117)
Accumulated Deficit
Organization and Summary of Significant Accounting Policies [Line Items]
Net loss									$ (95,186)	$ (68,334)	$ (54,568)
Cumulative effect of new accounting principle in period of adoption												(897)	$ (1,117)
Topic 842 | Accumulated Deficit
Organization and Summary of Significant Accounting Policies [Line Items]
Cumulative effect of new accounting principle in period of adoption												$ 900
Sanofi
Organization and Summary of Significant Accounting Policies [Line Items]
Revenues									22,680	13,516	12,258
Pfizer SB-525
Organization and Summary of Significant Accounting Policies [Line Items]
Revenues									39,359	$ 37,810	$ 17,008
Pfizer SB-525 | Change in collaboration agreement scope | Collaborative arrangement
Organization and Summary of Significant Accounting Policies [Line Items]
Revenues									5,700
Net loss									$ 5,700
Earnings per share, basic | $ / shares									$ 0.05
Minimum
Organization and Summary of Significant Accounting Policies [Line Items]
Estimated useful lives of related assets									3 years
Maximum
Organization and Summary of Significant Accounting Policies [Line Items]
Estimated useful lives of related assets									5 years

Organization and Summary of S_5

Organization and Summary of Significant Accounting Policies - Revenues from Strategic Partnering Collaboration Agreements and Research Activity Grants (Detail) - Revenue from Contract with Customer - Revenue From Collaboration Agreements, Grants And Licensing Concentration Risk [Member]	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Pfizer
Concentration Risk [Line Items]
Percentage of revenues	40.00%	47.00%	47.00%
Kite Pharma, Inc. ("Kite")
Concentration Risk [Line Items]
Percentage of revenues	34.00%	30.00%
Sanofi
Concentration Risk [Line Items]
Percentage of revenues	22.00%	16.00%	34.00%

Organization and Summary of S_6

Organization and Summary of Significant Accounting Policies - Reconciliation of Cash and Cash Equivalents (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Cash and cash equivalents	$ 80,428	$ 140,418	$ 49,826
Non-current restricted cash	1,500	3,500	3,500
Cash, cash equivalents and restricted cash as reported within the Consolidated Statements of Cash Flows	$ 81,928	$ 143,918	$ 53,326	$ 22,061

Organization and Summary of S_7

Organization and Summary of Significant Accounting Policies - Impact of Adoption of ASC on Condensed Consolidated Balance Sheet (Detail) - USD ($) $ in Thousands	Dec. 31, 2019	Jan. 01, 2019	Dec. 31, 2018
ASSETS
Property and equipment, net	$ 29,926		$ 78,723
Operating lease right-of-use assets	77,289		0
Prepaid rent			0
Liabilities:
Operating lease liabilities - current	3,214	$ 1,408	0
Deferred rent			271
Operating lease liabilities - long-term	41,192		0
Accumulated deficit	$ (656,985)		(562,696)
Topic 842
ASSETS
Property and equipment, net		16,223
Operating lease right-of-use assets		8,753
Prepaid rent		36,025
Liabilities:
Operating lease liabilities - current		1,408
Deferred rent		0
Operating lease liabilities - long-term		7,933
Accumulated deficit		(561,799)
Topic 842 | Adjustments Due to the Adoption of ASC Topic 842
ASSETS
Property and equipment, net		(62,500)
Operating lease right-of-use assets		8,753
Prepaid rent		36,025
Liabilities:
Deferred rent		(271)
Operating lease liabilities - long-term		7,933
Accumulated deficit		897
Build-to-Suit Leases
Liabilities:
Operating lease liabilities - long-term			$ 27,689
Build-to-Suit Leases | Topic 842
Liabilities:
Operating lease liabilities - long-term		0
Build-to-Suit Leases | Topic 842 | Adjustments Due to the Adoption of ASC Topic 842
Liabilities:
Operating lease liabilities - long-term		$ (27,689)

Fair Value Measurement - Summar

Fair Value Measurement - Summary of Fair Value Measurements of Cash Equivalents, Available-for-Sale Securities and Free Share Liability (Detail) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total marketable securities	$ 303,878	$ 259,715
Money market funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total cash equivalents	30,496	103,291
Commercial paper securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total cash equivalents	2,999
Total marketable securities	155,368	177,224
Corporate debt securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total marketable securities	95,017	63,870
U.S. government-sponsored entity debt securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total marketable securities	53,493	18,621
Fair value on recurring basis
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total cash equivalents	33,495	103,291
Total marketable securities	303,878	259,715
Total cash equivalents and marketable securities	337,373	363,006
Fair value on recurring basis | Money market funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total cash equivalents	30,496	103,291
Fair value on recurring basis | Commercial paper securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total cash equivalents	2,999
Total marketable securities	155,368	177,224
Fair value on recurring basis | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total cash equivalents	30,496	103,291
Total marketable securities	0	0
Total cash equivalents and marketable securities	30,496	103,291
Fair value on recurring basis | Level 1 | Money market funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total cash equivalents	30,496	103,291
Fair value on recurring basis | Level 1 | Commercial paper securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total cash equivalents	0
Total marketable securities	0	0
Fair value on recurring basis | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total cash equivalents	2,999	0
Total marketable securities	303,878	259,715
Total cash equivalents and marketable securities	306,877	259,715
Fair value on recurring basis | Level 2 | Money market funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total cash equivalents	0	0
Fair value on recurring basis | Level 2 | Commercial paper securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total cash equivalents	2,999
Total marketable securities	155,368	177,224
Fair value on recurring basis | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total cash equivalents	0	0
Total marketable securities	0	0
Total cash equivalents and marketable securities	0	0
Fair value on recurring basis | Level 3 | Money market funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total cash equivalents	0	0
Fair value on recurring basis | Level 3 | Commercial paper securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total cash equivalents	0
Total marketable securities	0	0
Fair value on recurring basis | Corporate debt securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total marketable securities	95,017	63,870
Fair value on recurring basis | Corporate debt securities | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total marketable securities	0	0
Fair value on recurring basis | Corporate debt securities | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total marketable securities	95,017	63,870
Fair value on recurring basis | Corporate debt securities | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total marketable securities	0	0
Fair value on recurring basis | U.S. government-sponsored entity debt securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total marketable securities	53,493	18,621
Fair value on recurring basis | U.S. government-sponsored entity debt securities | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total marketable securities	0	0
Fair value on recurring basis | U.S. government-sponsored entity debt securities | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total marketable securities	53,493	18,621
Fair value on recurring basis | U.S. government-sponsored entity debt securities | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total marketable securities	0	0
Fair value on recurring basis | Free shares asset
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total cash equivalents and marketable securities	236
Fair value on recurring basis | Free shares asset | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total cash equivalents and marketable securities	0
Fair value on recurring basis | Free shares asset | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total cash equivalents and marketable securities	0
Fair value on recurring basis | Free shares asset | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total cash equivalents and marketable securities	$ 236
Fair value on recurring basis | Free shares liability
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total liabilities		154
Fair value on recurring basis | Free shares liability | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total liabilities		0
Fair value on recurring basis | Free shares liability | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total liabilities		0
Fair value on recurring basis | Free shares liability | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total liabilities		$ 154

Fair Value Measurement - Additi

Fair Value Measurement - Additional Information (Detail) - USD ($) $ in Thousands	Oct. 01, 2018	Nov. 23, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Jul. 20, 2018
Debt Securities, Available-for-sale [Line Items]
Payments to acquire additional interest in subsidiaries			$ 262	$ 0	$ 0
Business acquisition, number of free shares outstanding subject to purchase (in shares)			366,000
TxCell S.A.
Debt Securities, Available-for-sale [Line Items]
Number of ordinary shares acquired (in shares)	13,519,036	11,528,635
TxCell S.A. | 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
Business acquisition estimated fair value liabilities of free shares						$ 200
Number of ordinary shares acquired (in shares)			111,000	25,047,671
Payments to acquire additional interest in subsidiaries			$ 300
Increase in fair value of free shares asset and liability			500
Estimated fair value of free shares			100
Business acquisition estimated fair value assets of free shares			$ 200
TxCell S.A. | Share Purchase Agreement and Tender Offer Agreement | Option Pricing Method
Debt Securities, Available-for-sale [Line Items]
Business acquisition estimated fair value liabilities of free shares				$ 200

Fair Value Measurement - Summ_2

Fair Value Measurement - Summary of Estimated Fair Value of Free Share Liability Assumptions (Detail)	12 Months Ended
	Dec. 31, 2019$ / shares	Dec. 31, 2018$ / shares	Dec. 31, 2019€ / shares	Oct. 01, 2018$ / shares
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
USD/ EUR Exchange Rate	0.91	0.87	0.91
Measurement Input, Share Price
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Sangamo Stock Price (USD) (in usd per share)	$ 8.68	$ 11.48
Stock Price Volatility Estimate
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Volatility Estimate	0.725	0.799	0.725
Exchange Rate Volatility Estimate
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Volatility Estimate	0.066	0.077	0.066
Risk Free Rate
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Risk Free Rate and Cost of Debt by Expected Exercise Date	Varies	Varies
TxCell S.A.
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Sangamo France Stock Price (EUR) (in Euro per share)				$ 2.99
TxCell S.A. | Measurement Input, Share Price
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Sangamo France Stock Price (EUR) (in Euro per share) | (per share)		$ 2.58	€ 2.14
TxCell S.A. | Stock Price Volatility Estimate
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Volatility Estimate	0.725	0.086	0.725
TxCell S.A. | Measurement Input Stock Price Correlation
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Estimated Correlation Sangamo and Sangamo France Stock Prices	1	0	1

Marketable Securities - Summary

Marketable Securities - Summary of Cash Equivalents and Available-for-Sale Securities (Detail) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Debt Securities, Available-for-sale [Line Items]
Cash and cash equivalents, at carrying value, total	$ 80,428	$ 140,418
Available-for-sale securities, amortized cost	303,546	259,974
Available-for-sale securities, gross unrealized gains	351	0
Available-for-sale securities, gross unrealized (Losses)	(19)	(259)
Available-for-sale securities, estimated fair value	303,878	259,715
Total cash equivalents and available-for-sale securities, amortized cost	337,040	363,265
Total cash equivalents and available-for-sale securities, gross unrealized gains	352	0
Total cash equivalents and available-for-sale securities, gross unrealized (losses)	(19)	(259)
Total cash equivalents and available-for-sale securities, estimated fair value	337,373	363,006
Money market funds
Debt Securities, Available-for-sale [Line Items]
Cash and cash equivalents, at carrying value, total	30,496	103,291
Cash equivalents, gross unrealized gains	0	0
Cash and cash equivalents accumulated gross unrealized loss before tax	0	0
Cash equivalents, estimated fair value	30,496	103,291
Commercial paper securities
Debt Securities, Available-for-sale [Line Items]
Cash and cash equivalents, at carrying value, total	2,998
Cash equivalents, gross unrealized gains	1
Cash and cash equivalents accumulated gross unrealized loss before tax	0
Cash equivalents, estimated fair value	2,999
Available-for-sale securities, amortized cost	155,230	177,353
Available-for-sale securities, gross unrealized gains	145	0
Available-for-sale securities, gross unrealized (Losses)	(7)	(129)
Available-for-sale securities, estimated fair value	155,368	177,224
Cash equivalents:
Debt Securities, Available-for-sale [Line Items]
Cash and cash equivalents, at carrying value, total	33,494	103,291
Cash equivalents, gross unrealized gains	1	0
Cash and cash equivalents accumulated gross unrealized loss before tax	0	0
Cash equivalents, estimated fair value	33,495	103,291
Corporate debt securities
Debt Securities, Available-for-sale [Line Items]
Available-for-sale securities, amortized cost	94,905	63,981
Available-for-sale securities, gross unrealized gains	115	0
Available-for-sale securities, gross unrealized (Losses)	(3)	(111)
Available-for-sale securities, estimated fair value	95,017	63,870
U.S. government-sponsored entity debt securities
Debt Securities, Available-for-sale [Line Items]
Available-for-sale securities, amortized cost	53,411	18,640
Available-for-sale securities, gross unrealized gains	91	0
Available-for-sale securities, gross unrealized (Losses)	(9)	(19)
Available-for-sale securities, estimated fair value	$ 53,493	$ 18,621

Marketable Securities - Summa_2

Marketable Securities - Summary of Available-for-Sale Securities by Contractual Maturity (Detail) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Investments, Debt and Equity Securities [Abstract]
Maturing in one year or less	$ 282,046	$ 259,715
Maturing after one year through five years	21,832	0
Total investments available-for-sale	$ 303,878	$ 259,715

Marketable Securities - Additio

Marketable Securities - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Investments, Debt and Equity Securities [Abstract]
Realized losses from the sale of available-for-sale securities	$ 0	$ 0	$ 0
Investments other-than-temporarily impaired	$ 0	$ 0

Major Customers, Partnerships_3

Major Customers, Partnerships and Strategic Alliances - Additional Information (Detail)	Apr. 05, 2018USD ($)	Sep. 30, 2019USD ($)	Aug. 31, 2019USD ($)	May 31, 2018USD ($)	Apr. 30, 2018USD ($)	Dec. 31, 2017USD ($)	May 31, 2017USD ($)	Jan. 31, 2014USD ($)program	Jan. 31, 2012USD ($)	Dec. 31, 2019USD ($)	Sep. 30, 2019USD ($)	Jun. 30, 2019USD ($)	Mar. 31, 2019USD ($)	Dec. 31, 2018USD ($)	Sep. 30, 2018USD ($)	Jun. 30, 2018USD ($)	Mar. 31, 2018USD ($)	Dec. 31, 2019USD ($)milestoneproductoption	Dec. 31, 2018USD ($)	Dec. 31, 2017USD ($)	Dec. 31, 2014USD ($)	Jan. 01, 2019USD ($)	Jan. 01, 2018USD ($)
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Agreement termination, term																		180 days
Cumulative-effect adjustment																						$ 897,000	$ 1,117,000
Revenues										$ 54,851,000	$ 21,958,000	$ 17,548,000	$ 8,071,000	$ 26,837,000	$ 23,562,000	$ 21,416,000	$ 12,637,000	$ 102,428,000	$ 84,452,000	$ 36,567,000
Other long-term liabilities										5,711,000				1,960,000				5,711,000	1,960,000
Accumulated Deficit
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Cumulative-effect adjustment																						$ 897,000	1,117,000
California Institute for Regenerative Medicine ("CIRM")
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Funds due under the agreement				$ 8,000,000
Other long-term liabilities										5,700,000				1,800,000				5,700,000	1,800,000
California Institute for Regenerative Medicine ("CIRM") | Research grants
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Revenues																		5,200,000
Kite Pharma, Inc. ("Kite")
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Revenues																		34,350,000	25,517,000
Kite Pharma, Inc. ("Kite") | Collaboration agreements
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Revenues																		$ 24,977,000	18,545,000
Kite Pharma, Inc. ("Kite") | Collaboration and license agreement
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Milestone payments received					$ 150,000,000
Initial research term of agreement																		6 years
Number of options to extend initial research term | option																		2
Extended research term of agreement																		1 year
Separate fee for additional term																		$ 10,000,000
Collaborative arrangement estimated reimbursable service costs for new research plan		$ 3,400,000
Collaborative arrangement transaction price		189,300,000
Revenues under agreement		150,000,000
Collaborative arrangement estimated reimbursable service costs		$ 39,300,000
Deferred revenue										106,500,000				131,500,000				106,500,000	131,500,000
Kite Pharma, Inc. ("Kite") | Collaboration and license agreement | Maximum
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Development and sales-based milestone payments to be received	$ 3,010,000,000
Kite Pharma, Inc. ("Kite") | Collaboration and license agreement | Achievement of specified research, clinical development, regulatory and first commercial sale milestones
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Contingent development - and sales-based milestone payments to be received	1,260,000,000
Kite Pharma, Inc. ("Kite") | Collaboration and license agreement | Achievement of specified sales-based milestones if annual worldwide net sales of licensed products reach specified levels
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Contingent development - and sales-based milestone payments to be received	$ 1,750,000,000
Pfizer SB-525
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Collaborative arrangement transaction price																		$ 105,000,000
Revenues under agreement							$ 70,000,000
Agreement termination, term																		15 years
Deferred revenue										4,000,000				10,000,000				$ 4,000,000	10,000,000
Revenues																		$ 39,359,000	37,810,000	17,008,000
Number of products approved | product																		0
Research service fees																		$ 80,000,000
Pfizer SB-525 | Topic 606
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Deferred Revenue																							(5,200,000)
Pfizer SB-525 | Topic 606 | Accumulated Deficit
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Cumulative-effect adjustment																							5,200,000
Pfizer SB-525 | SB-525
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Number of milestones included in transaction price | milestone																		0
Pfizer SB-525 | Collaboration agreements
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Revenues										8,700,000								$ 15,697,000	37,810,000	17,008,000
Contract with customer, liability, cumulative catch-up adjustment to revenue, change in measure of progress													$ 3,000,000
Pfizer SB-525 | Maximum | SB-525
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Milestone revenue receivable							300,000,000
Potential amount to be funded for achievement of specified commercialized and sales milestones							266,500,000
Pfizer SB-525 | Maximum | Other products
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Milestone revenue receivable							175,000,000
Pfizer SB-525 | Achievement of specified clinical development intellectual property and regulatory milestones | Maximum
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Development and sales-based milestone payments to be received							208,500,000
Pfizer SB-525 | Achievement of first commercial sale milestones | Maximum
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Development and sales-based milestone payments to be received							$ 475,000,000
Pfizer SB-525 | Amended collaboration and license agreement
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Deferred revenue										1,300,000								1,300,000
Milestone revenue receivable										25,000,000								25,000,000
Recognition of milestone																		$ 23,700,000
Pfizer C9ORF72
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Milestone payments received						$ 12,000,000
Agreement termination, term																		15 years
Pfizer C9ORF72 | Collaboration agreements
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Revenues																		$ 1,827,000	2,188,000	0
Pfizer C9ORF72 | C9ORF72
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Revenues under agreement						12,000,000
Deferred revenue										8,000,000				9,800,000				8,000,000	9,800,000
Pfizer C9ORF72 | Achievement of specified preclinical development clinical development and first commercial sale milestones | Maximum | C9ORF72
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Development and sales-based milestone payments to be received						60,000,000
Pfizer C9ORF72 | Achievement of commercial milestones | Maximum | C9ORF72
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Development and sales-based milestone payments to be received						90,000,000
Sanofi
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Revenues under agreement								$ 20,000,000
Revenues																		$ 22,680,000	13,516,000	12,258,000
Number of products approved | product																		0
Number of research programs | program								2
Sanofi | Topic 606
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Deferred Revenue																							(4,100,000)
Sanofi | Topic 606 | Accumulated Deficit
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Cumulative-effect adjustment																							$ 4,100,000
Sanofi | Collaboration agreements
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Revenues																		$ 3,494,000	4,013,000	1,769,000
Sanofi | Collaboration and license agreement
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Collaborative arrangement transaction price																		89,200,000
Revenues under agreement																		20,000,000
Collaborative arrangement estimated reimbursable service costs																		55,700,000
Deferred revenue										1,700,000				$ 4,600,000				$ 1,700,000	4,600,000
Number of milestones included in transaction price | milestone																		0
Recognition of milestone			$ 5,700,000															$ 7,100,000
Sanofi | Collaboration and license agreement | Milestone One
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Milestone payments received																		6,000,000
Milestone revenue receivable			$ 6,000,000
Sanofi | Collaboration and license agreement | Milestone Two
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Milestone revenue receivable										7,500,000								7,500,000
Sanofi | Collaboration and license agreement | Milestone Three
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Milestone revenue receivable										$ 13,500,000								13,500,000
Sanofi | Collaboration and license agreement | Maximum
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Development and sales-based milestone payments to be received								$ 276,300,000
Sanofi | Collaboration and license agreement | Achievement of specified clinical development and regulatory milestones | Maximum
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Development and sales-based milestone payments to be received								115,800,000
Sanofi | Collaboration and license agreement | Achievement of specified sales milestones | Maximum
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Development and sales-based milestone payments to be received								$ 160,500,000
Shire AG
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Revenues																		$ 0	$ 0	2,400,000
Shire AG | Collaboration and license agreement
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Revenues under agreement									$ 13,000,000
Agreement termination, term																		90 days
Deferred revenue						$ 2,300,000														$ 2,300,000
Recognition of milestone																					$ 1,000,000

Major Customers, Partnerships_4

Major Customers, Partnerships and Strategic Alliances - Revenues Recognized under Agreement (Detail) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Revenue related to Sanofi agreement:
Total	$ 54,851	$ 21,958	$ 17,548	$ 8,071	$ 26,837	$ 23,562	$ 21,416	$ 12,637	$ 102,428	$ 84,452	$ 36,567
Kite Pharma, Inc. ("Kite")
Revenue related to Sanofi agreement:
Total									34,350	25,517
Kite Pharma, Inc. ("Kite") | Recognition of upfront fee
Revenue related to Sanofi agreement:
Total									24,977	18,545
Kite Pharma, Inc. ("Kite") | Research services
Revenue related to Sanofi agreement:
Total									9,373	6,972
Sanofi
Revenue related to Sanofi agreement:
Total									22,680	13,516	12,258
Sanofi | Recognition of upfront fee
Revenue related to Sanofi agreement:
Total									3,494	4,013	1,769
Sanofi | Research services
Revenue related to Sanofi agreement:
Total									6,367	9,503	10,489
Sanofi | Milestone achievement
Revenue related to Sanofi agreement:
Total									12,819	0	0
Pfizer SB-525
Revenue related to Sanofi agreement:
Total									39,359	37,810	17,008
Pfizer SB-525 | Recognition of upfront fee
Revenue related to Sanofi agreement:
Total	$ 8,700								15,697	37,810	17,008
Pfizer SB-525 | Milestone achievement
Revenue related to Sanofi agreement:
Total									$ 23,662	$ 0	$ 0

Major Customers, Partnerships_5

Major Customers, Partnerships and Strategic Alliances - Agreement with Sigma-Aldrich Corporation - Additional Information (Detail) - USD ($) $ in Thousands	1 Months Ended	3 Months Ended								12 Months Ended
	Oct. 31, 2009	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2007
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Common stock issued under license agreement										$ 136,308	$ 215,758	$ 81,573
Revenues		$ 54,851	$ 21,958	$ 17,548	$ 8,071	$ 26,837	$ 23,562	$ 21,416	$ 12,637	102,428	84,452	36,567
Sigma-Aldrich Corporation
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Developed laboratory research reagents, research services period													3 years
Deferred revenue	$ 20,000
Common stock issued under license agreement	$ 4,900
Public offering, common stock shares issued	636,133
Reduced royalty rate	10.50%
Development and sales-based milestone payments to be received	$ 25,000
Revenues										$ 600	$ 500	$ 700
Sigma-Aldrich Corporation | License agreement terms
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Revenues under agreement	5,000
Sigma-Aldrich Corporation | License fee revenues
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Deferred revenue	$ 15,100

Major Customers, Partnerships_6

Major Customers, Partnerships and Strategic Alliances - Agreement with Dow AgroSciences in Plant Agriculture - Additional Information (Detail) - USD ($)

3 Months Ended

12 Months Ended

Dec. 31, 2019

Sep. 30, 2019

Jun. 30, 2019

Mar. 31, 2019

Dec. 31, 2018

Sep. 30, 2018

Jun. 30, 2018

Mar. 31, 2018

Dec. 31, 2019

Dec. 31, 2018

Dec. 31, 2017

Dec. 31, 2005

Research and Development Arrangement, Contract to Perform for Others [Line Items]

Revenues

$ 54,851,000

$ 21,958,000

$ 17,548,000

$ 8,071,000

$ 26,837,000

$ 23,562,000

$ 21,416,000

$ 12,637,000

$ 102,428,000

$ 84,452,000

$ 36,567,000

Dow Agro Sciences | License agreement terms

Research and Development Arrangement, Contract to Perform for Others [Line Items]

Research program to develop laboratory research reagents

3 years

One-time license fee earned on exercise of option

$ 6,000,000

Previously agreed research, development and commercialization milestone payments, and royalties on sales of products

$ 4,000,000

Percentage of royalties to be received from sublicensing

25.00%

Fee due

$ 25,300,000

Minimum license annual fees specific reckoning period

11 years

Dow Agro Sciences | License agreement terms | Minimum

Research and Development Arrangement, Contract to Perform for Others [Line Items]

Annual fees

$ 300,000

Dow Agro Sciences | License agreement terms | Maximum

Research and Development Arrangement, Contract to Perform for Others [Line Items]

Annual fees

3,000,000

Dow Agro Sciences | License agreement terms | Royalty revenues

Research and Development Arrangement, Contract to Perform for Others [Line Items]

Revenues

$ 2,300,000

Dow Agro Sciences | License agreement terms | License fee revenues

Research and Development Arrangement, Contract to Perform for Others [Line Items]

Revenues

$ 3,000,000

$ 3,000,000

$ 3,000,000

Acquisition of Sangamo France -

Acquisition of Sangamo France - Additional Information (Detail) - USD ($)	Oct. 01, 2018	Nov. 23, 2018	Sep. 30, 2019	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Jul. 20, 2018
Business Acquisition [Line Items]
Payments to acquire additional interest in subsidiaries				$ 262,000	$ 0	$ 0
Goodwill impairments				$ 0	$ 0
TxCell S.A.
Business Acquisition [Line Items]
Number of ordinary shares acquired (in shares)	13,519,036	11,528,635
Percentage of share capital and voting rights acquired					98.20%
Purchase price per share (in dollars per share)	$ 2.99
Number of shares not purchased by the acquirer	11,981,867
TxCell S.A. | SPA and TOA
Business Acquisition [Line Items]
Percentage of equity interests agreed to acquire							100.00%
Number of ordinary shares acquired (in shares)				111,000	25,047,671
Number of free shares held by the holders (in shares)							477,000
Payments to acquire additional interest in subsidiaries				$ 300,000
Business acquisition estimated fair value liabilities of free shares							$ 200,000
Business acquisition estimated fair value assets of free shares				200,000
TxCell S.A. | SPA and TOA | Option Pricing Method
Business Acquisition [Line Items]
Business acquisition estimated fair value liabilities of free shares					$ 200,000
TxCell S.A. | SPA and TOA | Former Executive of TxCell
Business Acquisition [Line Items]
Number of ordinary shares acquired (in shares)			52,700
Payments to acquire additional interest in subsidiaries				$ 100,000
TxCell S.A. | SPA
Business Acquisition [Line Items]
Number of ordinary shares acquired (in shares)	13,519,036
TxCell S.A. | SPA and TOA
Business Acquisition [Line Items]
Noncontrolling interest, ownership percentage by parent				98.70%

Acquisition of Sangamo France_2

Acquisition of Sangamo France - Summary of Estimated Fair Value of Net Assets Acquired (Detail) - USD ($) $ in Thousands	Oct. 01, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Business Acquisition [Line Items]
Goodwill		$ 39,273	$ 40,044	$ 1,585
TxCell S.A.
Business Acquisition [Line Items]
Consideration transferred	$ 45,911
Fair value of non-controlling interest	35,829
Fair value of Sangamo France	81,740
Cash	4,779
Current assets	2,427
Property and equipment	1,857
IPR&D	55,019
Other assets	155
Current liabilities	(9,761)
Assumed debt liabilities	(4,933)
Deferred tax liability, net	(6,798)
Fair value of net identifiable assets acquired	42,745
Goodwill	38,995
Total fair value of net assets acquired	$ 81,740

Acquisition of Sangamo France_3

Acquisition of Sangamo France - Summary of Non-controlling Interest (Detail) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Stockholders' Equity Attributable to Noncontrolling Interest
Stockholders' equity attributable to noncontrolling interest, beginning balance				$ 739					$ 739
Fair value of additional shares acquired									(321)
Net loss attributable to non-controlling interest	$ (54)	$ (54)	$ (72)	(53)	$ (555)	$ 0	$ 0	$ 0	(233)	$ (555)	$ 0
Stockholders' equity attributable to noncontrolling interest, ending balance	185				739				185	739
Non- Controlling Interest
Stockholders' Equity Attributable to Noncontrolling Interest
Stockholders' equity attributable to noncontrolling interest, beginning balance				$ 739					739
Stockholders' equity attributable to noncontrolling interest, ending balance	$ 185				$ 739				$ 185	$ 739

Other Balance Sheet Details (De

Other Balance Sheet Details (Detail) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 41,607	$ 88,033
Less: accumulated depreciation and amortization	(11,681)	(9,310)
Property and equipment, net	29,926	78,723
Laboratory equipment
Property, Plant and Equipment [Line Items]
Property and equipment, gross	17,179	11,466
Furniture and fixtures
Property, Plant and Equipment [Line Items]
Property and equipment, gross	4,639	3,840
Leasehold improvements
Property, Plant and Equipment [Line Items]
Property and equipment, gross	13,888	3,640
Buildings
Property, Plant and Equipment [Line Items]
Property and equipment, gross	0	3,876
Construction in progress
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 5,901	$ 65,211

Other Balance Sheet Details - S

Other Balance Sheet Details - Schedule of Intangible Assets and Goodwill (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Intangible Assets (Excluding Goodwill)
Balance, beginning of year	$ 54,243	$ 0
Indefinite-lived assets - IPR&D	0	55,019
Foreign currency translation adjustment	(1,087)	(776)
Balance, end of year	53,156	54,243
Goodwill
Goodwill, beginning balance	40,044	1,585
Goodwill acquired	0	38,995
Foreign currency translation adjustment	(771)	(536)
Goodwill, ending balance	$ 39,273	$ 40,044

Other Balance Sheet Details -_2

Other Balance Sheet Details - Summary of Accounts Payable and Accrued Liabilities (Detail) - USD ($) $ in Thousands	Dec. 31, 2019	Jan. 01, 2019	Dec. 31, 2018
Balance Sheet Related Disclosures [Abstract]
Accounts payable	$ 6,671		$ 3,355
Accrued research and development expenses	4,102		10,999
Accrued professional fees	1,118		1,930
Operating lease liabilities - current (included in Accounts payable and accrued liabilities on the Consolidated Balance Sheet)	3,214	$ 1,408	0
Deferred rent	0		204
Other	2,451		4,969
Total accounts payable and accrued liabilities	$ 17,556		$ 21,457

Commitments and Contingencies -

Commitments and Contingencies - Additional Information (Detail) $ in Millions	1 Months Ended	12 Months Ended
	Apr. 30, 2019USD ($)	Dec. 31, 2019USD ($)ft²	Dec. 31, 2018USD ($)	Dec. 31, 2017USD ($)
Commitments And Contingencies [Line Items]
Operating lease, cost		$ 7.9
Variable lease, cost		1.9
Operating lease, payments		3.5
Operating lease, expense		$ 7.9
Rent expenses			$ 2.3	$ 1.1
Operating lease, weighted average remaining lease term		8 years 9 months 18 days
Operating lease, weighted average discount rate, percent		6.20%
License obligations		$ 1.2
Manufacturing Capacity
Commitments And Contingencies [Line Items]
Payment to secure manufacturing capacity		3
Other commitment		6.3
Manufacturing Obligations
Commitments And Contingencies [Line Items]
Payment to secure manufacturing capacity	$ 0.5
Other commitment		$ 2
Non-cancelable Contractual Commitment
Commitments And Contingencies [Line Items]
Contractual obligation, paid upon execution	$ 0.5
Minimum
Commitments And Contingencies [Line Items]
Lease agreement, extendable lease term		5 years
Minimum | Non-cancelable Contractual Commitment
Commitments And Contingencies [Line Items]
Contractual obligation		$ 2.5
Maximum
Commitments And Contingencies [Line Items]
Lease agreement, extendable lease term		10 years
Brisbane, California
Commitments And Contingencies [Line Items]
Area of space leased (in sqft) | ft²		52,620
Lessee operating lease liability tenant improvement allowance		$ 6.8
Lessee operating lease, lease not yet commenced tenant improvement allowance		$ 10.2
Research and Office Space | Valbonne, France
Commitments And Contingencies [Line Items]
Area of space leased (in sqft) | ft²		20,800
Office And Laboratory | Brisbane, California
Commitments And Contingencies [Line Items]
Area of space leased (in sqft) | ft²		87,700
Office And Laboratory | Richmond, California
Commitments And Contingencies [Line Items]
Area of space leased (in sqft) | ft²		45,600
Office Space | Brisbane, California
Commitments And Contingencies [Line Items]
Area of space leased (in sqft) | ft²		35,080

Commitments and Contingencies_2

Commitments and Contingencies - Summary of Future Minimum Payments under Contractual Obligations (Detail) - USD ($) $ in Thousands	Dec. 31, 2019	Jan. 01, 2019	Dec. 31, 2018
Commitments and Contingencies Disclosure [Abstract]
2020	$ 5,870
2021	6,390
2022	6,468
2023	6,556
2024	6,694
Thereafter	26,141
Total lease payments	58,119
Imputed interest	(13,713)
Total	44,406
Operating lease liabilities - current (included in Accounts payable and accrued liabilities on the Consolidated Balance Sheet)	3,214	$ 1,408	$ 0
Operating lease liabilities - long-term	$ 41,192		$ 0

Stockholders' Equity - Addition

Stockholders' Equity - Additional Information (Detail) $ / shares in Units, $ in Thousands	1 Months Ended				12 Months Ended
	Apr. 30, 2019USD ($)$ / sharesshares	Jun. 30, 2018shares	Apr. 30, 2018USD ($)$ / sharesshares	Jun. 30, 2017USD ($)$ / sharesshares	Dec. 31, 2019USD ($)installment$ / sharesshares	Dec. 31, 2018USD ($)$ / sharesshares	Dec. 31, 2017USD ($)$ / sharesshares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Preferred shares authorized (in shares)					5,000,000	5,000,000
Net proceeds from issuance of common stock, after deducting offering expenses | $					$ 136,308	$ 215,758	$ 81,573
Stock option maximum term					6 years 6 months 14 days
Specified stockholder ownership percentage					10.00%
Purchase price of common stock percent under stock incentive plans for specified stockholder					110.00%
Stock option maximum term for specified stockholder					5 years
Share of common stock subject to a stock option or stock appreciation right (in shares)					100.00%
Additional equity award (in shares)					4,530,288
Intrinsic value of options exercised | $					$ 4,700	27,000	12,300
Options vested and expected to vest, aggregate intrinsic value | $					7,500	24,500	71,700
Options exercisable, aggregate intrinsic value | $					$ 5,442
Restricted stock units awarded (in shares)					834,745
Total payments for the employees' tax obligations to taxing authorities | $					$ 422	$ 254	$ 654
Shares reserved for issuance of future awards (in shares)					2,757,600
Share-Based Compensation Awards, Tranche 2
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock options granted vesting percentage					33.33%
Share-Based Compensation Awards, Tranche 3
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock options granted vesting percentage					33.33%
2013 Stock Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares reserved for issuance of future awards (in shares)					6,691,209
Amended and Restated 2013 Stock Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Additional equity award (in shares)			0
2018 Stock Incentive Plan
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%
Stock options vesting period					4 years
Stock options expiration term					10 years
Fixed ratio shares of common stock					1.33
2010 Employee Stock Purchase Plan
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%
Stock reserved for issuance under plan (in shares)		4,600,000
Purchase plan offering period		2 years
Purchase plan purchase period		6 months
Maximum | 2018 Stock Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock option maximum term					10 years
Employee Stock Options | 2018 Stock Incentive Plan | Share-Based Compensation Awards, Tranche 1
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock options granted vesting percentage					25.00%
Employee Stock Options | 2018 Stock Incentive Plan | Share-Based Compensation Awards, Tranche 2
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock options granted vesting percentage					2.08%
Restricted Stock Units (RSUs)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Restricted stock units awarded (in shares)					834,745	346,055	12,600
Grant date fair value per award of restricted stock units (in dollars per share) | $ / shares					$ 9.49	$ 17.87	$ 15.85
Share-based compensation arrangement by share-based payment award, number of vesting installment | installment					3
Aggregate fair value of RSUs vested in period | $					$ 2,000	$ 600	$ 1,200
Shares withheld from issuance in order to pay employee taxes (in shares)					39,160	20,193	42,243
Restricted Stock Units (RSUs) | Share-Based Compensation Awards, Tranche 1
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock options granted vesting percentage					33.33%
Common Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Issuance of common stock under public offering, net of issuance costs (in shares)	12,700,000		14,200,000	11,500,000	12,650,000	14,156,500	12,371,149
Public offering price of common stock issued (in dollars per share) | $ / shares	$ 11.50		$ 16.25	$ 7.25
Net proceeds from issuance of common stock, after deducting offering expenses | $	$ 136,300		$ 215,800	$ 78,100

Stockholders' Equity - Summary

Stockholders' Equity - Summary of Stock Option Activity (Detail) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2019USD ($)$ / sharesshares
Number of Shares
Options outstanding at beginning of period (in shares) | shares	8,726,092
Options granted (in shares) | shares	4,530,288
Options exercised (in shares) | shares	(806,226)
Options canceled (in shares) | shares	(2,620,867)
Options outstanding at end of period (in shares) | shares	9,829,287
Options vested and expected to vest at end of period (in shares) | shares	9,829,287
Options exercisable at end of period (in shares) | shares	3,993,645
Weighted- Average Exercise per Share Price
Options outstanding at beginning of period (in dollars per share) | $ / shares	$ 11.23
Options granted (in dollars per share) | $ / shares	9.68
Options exercised (in dollars per share) | $ / shares	5.08
Options canceled (in dollars per share) | $ / shares	12.39
Options outstanding at end of period (in dollars per share) | $ / shares	10.71
Options vested and expected to vest at end of period (in dollars per share) | $ / shares	10.71
Options exercisable at end of period (in dollars per share) | $ / shares	$ 10.43
Weighted-Average Remaining Contractual Term
Options outstanding at end of period (in years)	7 years 10 months 28 days
Options vested and expected to vest at end of period (in years)	7 years 10 months 28 days
Options exercisable at end of period (in years)	6 years 6 months 14 days
Aggregate Intrinsic Value
Options outstanding at end of period | $	$ 7,472
Options vested and expected to vest at end of period | $	7,472
Options exercisable at end of period | $	$ 5,442

Stockholders' Equity - Summar_2

Stockholders' Equity - Summary of Restricted Stock Unit Activity (Detail) $ in Thousands	12 Months Ended
	Dec. 31, 2019USD ($)shares
Number of Shares
RSUs outstanding at beginning of period (in shares)	322,701
RSUs awarded (in shares)	834,745
RSUs released (in shares)	(118,807)
RSUs forfeited (in shares)	(175,789)
RSUs outstanding at end of period (in shares)	862,850
RSUs vested and expected to vest at end of period (in shares)	862,850
Weighted-Average Remaining Contractual Term
RSUs outstanding at end of period (in years)	1 year 2 months 19 days
RSUs vested and expected to vest at end of period (in years)	1 year 2 months 19 days
Aggregate Intrinsic Value
RSUs outstanding at end of period | $	$ 7,222
RSUs vested and expected to vest at end of period | $	$ 7,222

Stock-Based Compensation - Stoc

Stock-Based Compensation - Stock-Based Compensation Expense (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock-based compensation expense	$ 19,330	$ 14,677	$ 9,089
Research and development
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock-based compensation expense	10,135	8,249	5,031
General and administrative
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock-based compensation expense	$ 9,195	$ 6,428	$ 4,058

Stock-Based Compensation - Addi

Stock-Based Compensation - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total compensation cost related to unvested stock options and RSU	$ 37,400,000
Weighted-average period of unvested stock options and RSU	2 years 9 months 3 days
Capitalized stock-based employee compensation expense	$ 0	$ 0	$ 0
Weighted-average estimated fair value per share of options granted (in dollars per share)	$ 6.37	$ 11.39	$ 4.10
Issuance of common stock under employee stock purchase plan (in shares)	249,364	328,710	253,994
Stock issued under employee stock purchase plans, average exercise price (in dollars per share)	$ 8.53	$ 4.51	$ 3.22
Weighted-average estimated fair value of shares purchased under ESPP plan (in dollars per share)	$ 4.70	$ 7.07	$ 2.37
Restricted Stock Units (RSUs)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total compensation cost related to unvested stock options and RSU	$ 7,000,000
Weighted-average period of unvested stock options and RSU	2 years 1 month 9 days

Stock-Based Compensation - Assu

Stock-Based Compensation - Assumptions Used for Estimating Fair Value of Employee Stock Options (Detail) - Employee Stock Options	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected dividend yield of stock	0.00%	0.00%	0.00%
Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Risk-free interest rate	2.53%	1.81%	1.13%
Expected term (in years)	5 years 7 months 2 days	5 years 8 months 23 days	5 years 3 months 10 days
Expected volatility	0.72%	0.71%	0.68%
Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Risk-free interest rate	2.96%	2.28%	1.61%
Expected term (in years)	5 years 7 months 9 days	5 years 9 months 29 days	5 years 3 months 14 days
Expected volatility	0.75%	0.72%	0.70%

Stock-Based Compensation - Weig

Stock-Based Compensation - Weighted-Average Assumptions Used for Estimating Fair Value of ESPP Purchased Rights (Detail) - 2010 Employee Stock Purchase Plan	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected dividend yield of stock	0.00%	0.00%	0.00%
Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Risk-free interest rate	2.16%	0.44%	0.41%
Expected term (in years)	6 months	6 months	6 months
Expected volatility	0.73%	0.66%	0.71%
Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Risk-free interest rate	2.80%	0.76%	0.80%
Expected term (in years)	2 years	2 years	2 years
Expected volatility	0.83%	0.82%	0.76%

Employee Benefit Plan - Additio

Employee Benefit Plan - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Retirement Benefits [Abstract]
Defined contribution plan, employer's matching contribution percent	50.00%	50.00%	50.00%
Maximum percentage limit of employee contributions	8.00%	8.00%	8.00%
Defined contribution plan, maximum employer's contribution per employee	$ 4,000
Aggregate employer's contributions to defined contribution plan	$ 900,000	$ 800,000	$ 500,000

Income Taxes - Summary of Domes

Income Taxes - Summary of Domestic and Foreign Components of Loss Before Income Taxes (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Income Tax Disclosure [Abstract]
Domestic	$ (77,354)	$ (65,695)	$ (54,568)
Foreign	(18,065)	(3,194)	0
Loss before income taxes	$ (95,419)	$ (68,889)	$ (54,568)

Income Taxes - Summary of Benef

Income Taxes - Summary of Benefit for Income Taxes (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Current:
Federal	$ 0	$ 0	$ 0
State	0	0	0
Foreign	0	0	0
Subtotal	0	0	0
Deferred:
Federal	0	0	0
State	0	0	0
Foreign	0	0	0
Subtotal	0	0	0
Income tax benefit	$ 0	$ 0	$ 0

Income Taxes - Additional Infor

Income Taxes - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Income Taxes [Line Items]
Increase (decrease) in deferred tax assets valuation allowance	$ (29,600,000)	$ 45,300,000	$ (28,900,000)
Deferred tax assets, net operating loss carryforwards for federal	489,400,000
Deferred tax assets, net operating loss carryforwards for state	164,700,000
Federal research tax credit carryforwards	16,400,000
State research tax credit carryforwards	15,200,000
Accrued interest and/or penalties	0
French
Income Taxes [Line Items]
Deferred tax assets, net operating loss carryforwards for foreign	$ 147,900,000

Income Taxes - Schedule of Diff

Income Taxes - Schedule of Difference Between Benefit for Income Taxes and Federal Statutory Income Tax Rate (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Income Tax Disclosure [Abstract]
Tax at federal statutory rate(1)	$ (20,038)	$ (14,467)	$ (18,553)
State taxes, net	(9,597)	(2,849)	795
Federal rate change	0	0	53,045
Foreign rate differential	(665)	(177)	0
Non-deductible stock-based compensation	2,817	(2,729)	2,120
Research credits	(3,429)	(1,005)	(869)
Change in valuation allowance	29,655	20,271	(36,575)
Other	1,257	956	37
Income tax benefit	$ 0	$ 0	$ 0

Income Taxes - Schedule of Di_2

Income Taxes - Schedule of Difference Between Benefit for Income Taxes and Federal Statutory Income Tax Rate, Additional Information (Detail)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Income Tax Disclosure [Abstract]
Statutory tax rate	21.00%	21.00%	35.00%

Income Taxes - Schedule of Comp

Income Taxes - Schedule of Company's Deferred Tax Assets (Detail) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Deferred tax assets:
Net operating loss carryforwards	$ 133,765	$ 138,896
Research and development tax credit carryforwards	21,459	16,829
Stock-based compensation	4,194	3,801
Deferred revenue	32,171	3,191
Fixed assets	11,282	0
Deferred Tax Assets, Lease Liability	11,722	0
Build to suit lease liability	0	6,400
Accruals and reserves	675	0
Other	151	604
Total deferred tax asset	215,419	169,721
Valuation allowance	187,724	158,150
Net deferred tax assets	27,695	11,571
Liabilities:
Intangible assets	(13,609)	(14,100)
Operating lease right-of-use assets	20,656
Fixed assets	0	(4,176)
Net deferred tax liability	(34,265)	(18,276)
Total deferred tax liability	$ (6,570)	$ (6,705)

Income Taxes - Summary of Activ

Income Taxes - Summary of Activity Related to Company's Unrecognized Tax Benefits (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Beginning balance	$ 6,288	$ 5,659	$ 5,045
Additions based on tax positions related to the current year	5,393	636	622
Additions for tax positions of prior years	(51)	(7)	(8)
Reductions for tax positions of prior years	0	0	0
Ending balance	$ 11,630	$ 6,288	$ 5,659

Related Party Disclosures (Deta

Related Party Disclosures (Details) - USD ($) $ in Thousands	Oct. 01, 2018	Nov. 23, 2018	Sep. 30, 2019	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Related Party Transaction [Line Items]
Payments to acquire additional interest in subsidiaries				$ 262	$ 0	$ 0
TxCell S.A.
Related Party Transaction [Line Items]
Number of ordinary shares acquired (in shares)	13,519,036	11,528,635
TxCell S.A. | Share Purchase Agreement and Tender Offer Agreement
Related Party Transaction [Line Items]
Number of ordinary shares acquired (in shares)				111,000	25,047,671
Payments to acquire additional interest in subsidiaries				$ 300
Former Executive of TxCell | TxCell S.A. | Share Purchase Agreement and Tender Offer Agreement
Related Party Transaction [Line Items]
Number of ordinary shares acquired (in shares)			52,700
Payments to acquire additional interest in subsidiaries				$ 100

Quarterly Financial Data (Una_3

Quarterly Financial Data (Unaudited) - Summary of Quarterly Financial Data (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Quarterly Financial Information Disclosure [Abstract]
Revenues	$ 54,851	$ 21,958	$ 17,548	$ 8,071	$ 26,837	$ 23,562	$ 21,416	$ 12,637	$ 102,428	$ 84,452	$ 36,567
Operating expenses	53,382	51,206	51,052	51,968	47,609	39,803	40,556	33,634	207,608	161,602	92,928
Net loss	4,501	(27,361)	(30,356)	(42,203)	(19,219)	(12,843)	(16,640)	(20,187)	(95,419)	(68,889)	(54,568)
Net loss attributable to non-controlling interest	(54)	(54)	(72)	(53)	(555)	0	0	0	(233)	(555)	0
Net (loss) income attributable to Sangamo Therapeutics, Inc.	$ 4,555	$ (27,307)	$ (30,284)	$ (42,150)	$ (18,664)	$ (12,843)	$ (16,640)	$ (20,187)	$ (95,186)	$ (68,334)	$ (54,568)
Basic and diluted net (loss) income per share attributable to Sangamo Therapeutics, Inc. (in dollars per share)	$ 0.04	$ (0.24)	$ (0.26)	$ (0.41)	$ (0.18)	$ (0.13)	$ (0.17)	$ (0.23)	$ (0.85)	$ (0.70)	$ (0.70)

Subsequent Events (Details)

Subsequent Events (Details) - Subsequent Event	1 Months Ended	11 Months Ended
	Feb. 28, 2020USD ($)product_target$ / shares	Dec. 31, 2020USD ($)shares
Subsequent Event [Line Items]
Agreement restriction, ownership percentage (less than)	5.00%
Biogen MA Inc | Collaboration and license agreement
Subsequent Event [Line Items]
Number of neurological disease gene targets | product_target	12
Number of product targets selected | product_target	3
Number of additional neurological disease gene targets | product_target	9
Target selection period	5 years
Biogen MA Inc | Collaboration and license agreement | Forecast
Subsequent Event [Line Items]
Proceeds from collaborators		$ 125,000,000
Biogen MA Inc | Collaboration and license agreement | Pre-approval Milestone
Subsequent Event [Line Items]
Maximum milestone payment receivable	$ 925,000,000
Biogen MA Inc | Collaboration and license agreement | Sales-based Milestone
Subsequent Event [Line Items]
Maximum milestone payment receivable	1,445,000,000
Biogen MA Inc | Collaboration and license agreement | Achievement of specified research, clinical development, regulatory and first commercial sale milestones
Subsequent Event [Line Items]
Maximum milestone payment receivable	$ 2,370,000,000
Biogen MA Inc | Stock Purchase Agreement
Subsequent Event [Line Items]
Agreement restriction expiration period	3 years
Agreement restriction, percentage of shares held	50.00%
Agreement provision, expiration period	2 years
Agreement provision, ownership percentage (less than)	5.00%
Biogen MA Inc | Stock Purchase Agreement | Forecast
Subsequent Event [Line Items]
Sale of stock, number of shares issued in transaction (in shares) | shares		24,420,157
Sale of stock, price per share (in dollars per share) | $ / shares	$ 9.2137
Consideration received from sale of stock		$ 225,000,000