Net Loss Per Share Attributable to Common Stockholders - Schedule of Basic and Diluted Net Loss Per Share and Per Unit (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Numerator:
Net loss applicable to common stockholders and members	$ (4,111)	$ (2,150)
Denominator:
Weighted-average basic and diluted common shares and common units	14,417,649	10,307,379
Basic and diluted net loss per common share and common unit	$ (0.29)	$ (0.21)