Business - Additional Information (Detail) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Cash and cash equivalents	$ 100,056	$ 115,069
Accumulated deficit	$ 785,655	$ 764,101
Common Stock, Shares Authorized	250,000,000	250,000,000
Common Stock, Shares, Outstanding	215,257,674	214,591,906
Common Stock [Member]
Common Stock, Shares Authorized	250,000,000
Common Stock, Shares, Outstanding	215,525,411
Common stock reserved for future issuance	33,965,938