Background and Organization - Additional Information (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2019
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Net loss	$ (28,125)	$ (20,831)	$ (81,809)	$ (84,990)
Net cash used from operations			(59,680)	$ (76,632)
Cash and cash equivalents	$ 163,881		$ 163,881		$ 226,783