Net Loss per Share - Computation of Denominators Used in Net Loss per Share (Detail) - shares
12 Months Ended
Dec. 31, 2016
Dec. 31, 2015
Dec. 31, 2014
Basic:      
Weighted average shares outstanding 27,279,008 24,620,372 20,965,935
Diluted:      
Weighted average shares outstanding - Basic 27,279,008 24,620,372 20,965,935
Common stock options 0 0 0
Denominator for diluted net loss per share 27,279,008 24,620,372 20,965,935