Condensed Consolidated Statements of Stockholders Equity (Unaudited) - USD ($) $ in Thousands	Total	Common Stock Common Class A	Common Stock Common Class B	Additional Paid In Capital	Accumulated Other Comprehensive Income	Accumulated Deficit
Balance (in shares) at Dec. 31, 2018		80,769,763	19,310,465
Balance at Dec. 31, 2018	$ 438,235	$ 80	$ 20	$ 808,527	$ 1,282	$ (371,674)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net loss	(36,503)					(36,503)
Exercises of stock options (in shares)		748,679	1,023,984
Exercises of stock options	15,328	$ 1	$ 1	15,326
Vesting of early exercised stock options	9			9
Vesting of restricted stock units (in shares)		641,406	39,360
Value of equity awards withheld for tax liability (in shares)		(5,860)	(4,431)
Value of equity awards withheld for tax liability	(1,062)			(1,062)
Conversion of shares of Class B common stock into shares of Class A common stock (in shares)		4,339,519	(4,339,519)
Conversion of shares of Class B common stock into shares of Class A common stock		$ 4	$ (4)
Equity awards assumed in acquisition	191,620			191,620
Net unrealized (loss) gain on marketable securities, net of tax	1,041				1,041
Shares issued in acquisition (in shares)		23,555,081
Shares issued in acquisition	2,658,898	$ 24		2,658,874
Stock-based compensation	59,947			59,947
Balance (in shares) at Mar. 31, 2019		110,048,588	16,029,859
Balance at Mar. 31, 2019	3,327,513	$ 109	$ 17	3,733,241	2,323	(408,177)
Balance (in shares) at Dec. 31, 2019		126,882,172	11,530,627
Balance at Dec. 31, 2019	4,279,411	$ 124	$ 14	4,952,999	5,086	(678,812)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net loss	(94,791)					(94,791)
Exercises of stock options (in shares)		243,029	426,001
Exercises of stock options	8,231			8,231
Vesting of restricted stock units (in shares)		849,763	23,107
Vesting of restricted stock units	1	$ 1
Value of equity awards withheld for tax liability (in shares)		(8,726)	(4,692)
Value of equity awards withheld for tax liability	(1,674)			(1,674)
Conversion of shares of Class B common stock into shares of Class A common stock (in shares)		618,103	(618,103)
Conversion of shares of Class B common stock into shares of Class A common stock		$ 1	$ (1)
Donated common stock (in shares)		22,102
Donated common stock	2,701			2,701
Net unrealized (loss) gain on marketable securities, net of tax	(9,375)				(9,375)
Stock-based compensation	72,021			72,021
Balance (in shares) at Mar. 31, 2020		128,606,443	11,356,940
Balance at Mar. 31, 2020	$ 4,256,525	$ 126	$ 13	$ 5,034,278	$ (4,289)	$ (773,603)