Nature of the Business - Additional Information (Detail) $ in Thousands	6 Months Ended
	Jun. 30, 2020 USD ($) Disease	Dec. 31, 2019 USD ($)
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Number of rare diseases | Disease	1,800
Accumulated deficit	$ (158,852)	$ (137,019)
Cash, cash equivalents and marketable securities	$ 37,116	$ 56,276