CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE LOSS - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Statement of Comprehensive Income [Abstract]
Net loss	$ (35,965)	$ (30,356)	$ (78,939)	$ (72,559)
Foreign currency translation adjustment	1,783	1,442	150	(62)
Change in unrealized gain on available-for-sale securities	392	484	646	737
Comprehensive loss	(33,790)	(28,430)	(78,143)	(71,884)
Comprehensive loss attributable to non-controlling interest	(36)	(72)	(97)	(125)
Comprehensive loss attributable to Sangamo Therapeutics, Inc.	$ (33,754)	$ (28,358)	$ (78,046)	$ (71,759)