Background and Organization - Additional Information (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Net loss	$ (120,199)	$ (76,396)	$ (72,176)
Net cash used from operations	(79,567)	(122,194)	$ (70,053)
Cash and cash equivalents	$ 226,783	$ 167,432