CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE LOSS - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Statement of Comprehensive Income [Abstract]
Net loss	$ (47,688)	$ (1,508)	$ (140,801)	$ (80,447)
Foreign currency translation adjustment, net of tax	(2,565)	3,839	(6,006)	3,989
Unrealized (loss) gain on marketable securities, net of tax	(45)	(633)	(36)	13
Comprehensive (loss) income	(50,298)	1,698	(146,843)	(76,445)
Comprehensive income (loss) attributable to non-controlling interest	0	42	(11)	(55)
Comprehensive (loss) income attributable to Sangamo Therapeutics, Inc.	$ (50,298)	$ 1,656	$ (146,832)	$ (76,390)