CONDENSED CONSOLIDATED STATEMENTS OF CONVERTIBLE PREFERRED STOCK AND STOCKHOLDERS’ EQUITY (DEFICIT) - USD ($) $ in Thousands	Total	Common Class B	Convertible Preferred Stock	Common Stock	Common Stock Common Class A	Common Stock Common Class B	Additional Paid-in Capital	Treasury Stock	Accumulated Other Comprehensive Income (Loss)	Accumulated Deficit
Convertible Preferred Stock, beginning balance (in shares) at Dec. 31, 2018			53,630,213
Convertible Preferred Stock, beginning balance at Dec. 31, 2018			$ 219,584
Convertible Preferred Stock, ending balance (in shares) at Mar. 31, 2019			53,630,213
Convertible Preferred Stock, ending balance at Mar. 31, 2019			$ 219,584
Beginning balance (in shares) at Dec. 31, 2018				25,025,836
Beginning balance at Dec. 31, 2018	$ (131,927)			$ 1			$ 16,403	$ (2,109)	$ (36)	$ (146,186)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Exercise of stock options (in shares)				449,751
Exercise of stock options	639						639
Vesting of early exercised stock options (in shares)				40,524
Vesting of early exercised stock options	155						155
Stock-based compensation	1,467						1,467
Repayment of stockholder note (in shares)				5,297
Repayment of stockholder note	12						12
Net loss	(9,727)									(9,727)
Other comprehensive income	56								56
Ending balance (in shares) at Mar. 31, 2019				25,521,408
Ending balance at Mar. 31, 2019	(133,598)			$ 1			18,676	$ (2,109)	20	(150,186)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Impact of change in accounting policy	$ 5,727
Convertible Preferred Stock, beginning balance (in shares) at Dec. 31, 2019	0
Convertible Preferred Stock, ending balance (in shares) at Mar. 31, 2020	0
Beginning balance (in shares) at Dec. 31, 2019					60,954,694	33,863,021
Beginning balance at Dec. 31, 2019	$ 257,652				$ 1	$ 1	449,463		196	(192,009)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Exercise of stock options (in shares)	1,107,000				1,106,688	0
Exercise of stock options	$ 3,174						3,174
Vesting of early exercised stock options (in shares)						36,590
Vesting of early exercised stock options	146						146
Stock-based compensation	6,577						6,577
Conversion of Class B to Class A Stock (in shares)		53,600,000			9,727,897	9,727,897
Net loss	(11,990)									(11,990)
Other comprehensive income	491								491
Ending balance (in shares) at Mar. 31, 2020					71,789,279	24,171,714
Ending balance at Mar. 31, 2020	256,050				$ 1	$ 1	$ 459,360		$ 687	$ (203,999)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Impact of change in accounting policy	$ 0