Acquisition of Sangamo France - Summary of Non-controlling Interest (Detail) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Stockholders' Equity Attributable to Noncontrolling Interest
Stockholders' equity attributable to noncontrolling interest, beginning balance				$ 185					$ 185
Fair value of additional shares acquired									(927)
Net loss attributable to non-controlling interest	$ (71)	$ 42	$ (36)	(61)	$ (54)	$ (54)	$ (72)	$ (53)	(126)	$ (233)	$ (555)
Stockholders' equity attributable to noncontrolling interest, ending balance	(868)				185				(868)	185
Non- Controlling Interest
Stockholders' Equity Attributable to Noncontrolling Interest
Stockholders' equity attributable to noncontrolling interest, beginning balance				$ 185					185
Stockholders' equity attributable to noncontrolling interest, ending balance	$ (868)				$ 185				$ (868)	$ 185