Prepaid Expenses and Other Current Assets (Detail) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Deferred Costs Capitalized Prepaid And Other Assets Disclosure [Abstract]
Prepaid insurance	$ 648	$ 502
Prepaid research and development	11,989	122
Other prepaid	390	597
Other current assets	648	388
Total	$ 13,675	$ 1,609