Net Loss per Share Attributable to Common Stock - Computation of Net Loss Per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Numerator:
Net income (loss)	$ 34,166	$ 6,782	$ (32,562)	$ (73,023)
Dividend on convertible preferred stock	1,530	0	2,814	0
Undistributed earnings attributable to participating securities	(653)	0	0	0
Net income (loss) attributable to common stock - basic	31,983	6,782	(35,376)	(73,023)
Net income (loss) attributable to common stock - diluted	$ 31,983	$ 6,782	$ (35,376)	$ (73,023)
Denominator:
Weighted average shares - basic (in shares)	99,840,144	91,994,731	97,365,122	91,279,086
Dilutive shares from stock plans (in shares)	7,767,567	5,176,539	0	0
Weighted averages shares - diluted (in shares)	107,607,711	97,171,270	97,365,122	91,279,086
Net income (loss) per share:
Net income (loss) attributable to common stock - basic (in dollars per share)	$ 0.32	$ 0.07	$ (0.36)	$ (0.80)
Net income (loss) attributable to common stock - diluted (in dollars per share)	$ 0.30	$ 0.07	$ (0.36)	$ (0.80)