Net Loss Per Share - Basic and diluted net loss per share (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Numerator:
Net loss attributable to common stockholders for earnings per share, basic and diluted	$ 67,484	$ 37,940
Denominator:
Shares used to compute net loss per share, basic and diluted	15,834,175	2,104,861
Basic and diluted net loss attributable to common stockholders per share	$ 4.26	$ 18.02