Net Loss per Share - Computation of Denominators Used in Net Loss per Share (Detail) - shares	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Basic:
Weighted average common shares outstanding	42,669,333	35,892,786	31,202,842
Diluted:
Weighted average common shares outstanding - Basic	42,669,333	35,892,786	31,202,842
Common stock options	0	0	0
Denominator for diluted net loss per share	42,669,333	35,892,786	31,202,842