Net Loss Per Share Attributable to Common Stockholders - Computation of EPS (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Class of Stock [Line Items]
Weighted-average shares used in computing net loss per share attributable to common stockholders, basic and diluted (in shares)	95,401	25,290
Net loss per share attributable to common shareholders, basic and diluted (in USD per share)	$ (0.13)	$ (0.38)
Common Class A
Class of Stock [Line Items]
Net loss attributable to common stockholders	$ (8,196)
Weighted-average shares used in computing net loss per share attributable to common stockholders, basic and diluted (in shares)	65,210
Net loss per share attributable to common shareholders, basic and diluted (in USD per share)	$ (0.13)
Shares issued (in shares)	12,900
Common Class B
Class of Stock [Line Items]
Net loss attributable to common stockholders	$ (3,794)	$ (9,727)
Weighted-average shares used in computing net loss per share attributable to common stockholders, basic and diluted (in shares)	30,191	25,290
Net loss per share attributable to common shareholders, basic and diluted (in USD per share)	$ (0.13)	$ (0.38)
Number of shares converted (in shares)	53,600