Net Income (Loss) Per Share - Computation of Basic and Diluted Net Loss Per Share Attributable to Common Stockholders (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended				6 Months Ended
	Jun. 30, 2020	Mar. 31, 2020	Jun. 30, 2019	Mar. 31, 2019	Jun. 30, 2020	Jun. 30, 2019
Earnings Per Share [Abstract]
Net income (loss)	$ 13,224	$ (41,248)	$ (322)	$ (5,242)	$ (28,024)	$ (5,564)
Accretion of redeemable preferred stock	(5,644)		(4,777)		(11,059)	(9,311)
Net income (loss) attributable to common stockholders - basic and diluted	$ 7,580		$ (5,099)		$ (39,083)	$ (14,875)
Weighted-average common shares outstanding - basic	10,649		8,647		9,718	8,602
Net income (loss) per share attributable to common stockholders - basic	$ 0.71		$ (0.59)		$ (4.02)	$ (1.73)
Weighted-average common shares outstanding - diluted	19,139		8,647		9,718	8,602
Net income (loss) per share attributable to common stockholders - diluted	$ 0.40		$ (0.59)		$ (4.02)	$ (1.73)