Schedule of Collaborative Revenues Under Collaboration Agreement (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Disaggregation Of Revenue [Line Items]
Total revenues	$ 1,920	$ 784
Collaborative Arrangements
Disaggregation Of Revenue [Line Items]
Total revenues	854	784
EUSA | Collaborative Arrangements
Disaggregation Of Revenue [Line Items]
Total revenues	$ 854	$ 784