Condensed Consolidated Statements of Comprehensive Loss - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Statement of Comprehensive Income [Abstract]
Net loss	$ (27,361)	$ (12,843)	$ (99,920)	$ (49,670)
Foreign currency translation adjustment	(4,077)	0	(4,139)	0
Change in unrealized (loss) gain on available-for-sale securities	(59)	(87)	678	42
Comprehensive loss	(31,497)	(12,930)	(103,381)	(49,628)
Comprehensive loss attributable to non-controlling interest	(54)	0	(179)	0
Comprehensive loss attributable to Sangamo Therapeutics, Inc.	$ (31,443)	$ (12,930)	$ (103,202)	$ (49,628)