Net Income (Loss) per Share - Calculation of Basic and Diluted Net Income (Loss) per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Numerator:
Net income (loss)									$ (12,884)	$ 13,938	$ 1,837
Income allocated to participating securities									0	(4,415)	(1,837)
Net income (loss) attributable to common stockholders	$ (10,716)	$ (778)	$ (155)	$ (1,235)	$ 2,360	$ 4,009	$ 3,154	$ 0	$ (12,884)	$ 9,523	$ 0
Denominator:
Weighted-average shares, basic (in shares)									37,119	24,862	2,735
Weighted-average common shares outstanding, diluted (in shares)									37,119	29,959	2,735
Net income (loss) per share attributable to common stockholders:
Basic (in dollars per share)	$ (0.29)	$ (0.02)	$ 0.00	$ (0.03)	$ 0.06	$ 0.11	$ 0.13	$ 0.00	$ (0.35)	$ 0.38	$ 0.00
Diluted (in dollars per share)	$ (0.29)	$ (0.02)	$ 0.00	$ (0.03)	$ 0.06	$ 0.10	$ 0.11	$ 0.00	$ (0.35)	$ 0.32	$ 0.00
Restricted stock units and awards
Denominator:
Dilutive effect of share-based payment arrangements (in shares)									0	11	0
Common stock options
Denominator:
Dilutive effect of share-based payment arrangements (in shares)									0	5,086	0