Background and Organization - Additional Information (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2019
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Net loss	$ (26,152)	$ (30,798)	$ (53,684)	$ (64,159)
Net cash used from operations			(45,018)	$ (49,552)
Cash and cash equivalents	$ 179,514		$ 179,514		$ 226,783