Consolidated Statements of Stockholders Equity - USD ($) $ in Thousands	Total	Common Class A	Common Class B	Common Stock Common Class A	Common Stock Common Class B	Additional Paid In Capital	Accumulated Other Comprehensive Income	Accumulated Deficit	Follow-on Public Offering	Follow-on Public Offering Common Stock Common Class A	Follow-on Public Offering Additional Paid In Capital
Balance (in shares) at Dec. 31, 2016				49,996,410	37,252,138
Balance at Dec. 31, 2016	$ 329,447			$ 51	$ 36	$ 516,090	$ 0	$ (186,730)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net loss	(63,708)							(63,708)
Exercises of vested stock options (in shares)				0	5,186,539
Exercises of vested stock options	25,597			$ 0	$ 6	25,591
Vesting of early exercised stock options	378					378
Vesting of restricted stock units (in shares)				360,116	351,255
Vesting of restricted stock units	0			$ 0
Value of equity awards withheld for tax liability (in shares)					(22,538)
Value of equity awards withheld for tax liability	(678)					(678)
Exercises of unvested stock options (in shares)					22,510
Conversion of shares of Class B common stock into shares of Class A common stock (in shares)				18,710,499	(18,710,499)
Conversion of shares of Class B common stock into shares of Class A common stock				$ 18	$ (18)
Shares issued under ESPP (in shares)				794,142
Shares issued under ESPP	11,918			$ 1		11,917
Donated common stock (in shares)				45,383
Donated common stock	1,172					1,172
Repurchases of unvested stock options (in shares)					(16,159)
Repurchases of unvested stock options	(100)					(100)
Unrealized gain (loss) on marketable securities, net of tax	(598)						(598)
Foreign currency translation	2,623						2,623
Stock-based compensation	53,795					53,795
Balance (in shares) at Dec. 31, 2017				69,906,550	24,063,246
Balance at Dec. 31, 2017	359,846			$ 70	$ 24	608,165	2,025	(250,438)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net loss	(121,949)							(121,949)
Adjustment to opening retained earnings due to adoption of ASC 606	713							713
Exercises of vested stock options (in shares)				0	3,625,991
Exercises of vested stock options	29,736			$ 0	$ 4	29,732
Vesting of early exercised stock options	36					36
Vesting of restricted stock units (in shares)				1,970,565	172,211
Vesting of restricted stock units	2			$ 2
Value of equity awards withheld for tax liability (in shares)				(25,932)	(22,044)
Value of equity awards withheld for tax liability	(2,654)					(2,654)
Exercises of unvested stock options (in shares)					2,041
Conversion of shares of Class B common stock into shares of Class A common stock (in shares)				8,530,980	(8,530,980)
Conversion of shares of Class B common stock into shares of Class A common stock				$ 8	$ (8)
Shares issued under ESPP (in shares)				325,262
Shares issued under ESPP	10,122					10,122
Donated common stock (in shares)				62,338
Donated common stock	5,996					5,996
Unrealized gain (loss) on marketable securities, net of tax	258						258
Issuance of debt conversion option	119,435					119,435
Debt conversion option issuance costs	(2,819)					(2,819)
Capped call option issuance costs	(58,465)					(58,465)
Foreign currency translation	(1,001)						(1,001)
Stock-based compensation	98,979					98,979
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	(307,063)							(307,063)
Exercises of vested stock options (in shares)				1,466,813	2,154,053
Exercises of vested stock options	37,742			$ 1	$ 2	37,739
Recapitalization of a subsidiary	0					75		(75)
Vesting of early exercised stock options	21					21
Vesting of restricted stock units (in shares)				2,775,788	117,331
Vesting of restricted stock units	3			$ 2	$ 1
Value of equity awards withheld for tax liability (in shares)				(23,543)	(22,095)
Value of equity awards withheld for tax liability	(5,412)					(5,412)
Conversion of shares of Class B common stock into shares of Class A common stock (in shares)				10,029,127	(10,029,127)
Conversion of shares of Class B common stock into shares of Class A common stock				$ 9	$ (9)
Shares issued under ESPP (in shares)				244,628
Shares issued under ESPP	19,738					19,738
Equity awards assumed in acquisition	182,554					182,554
Unrealized gain (loss) on marketable securities, net of tax	3,804						3,804
Shares issued in acquisition (in shares)				23,555,081						8,064,515
Shares issued in acquisition	2,658,898			$ 24		2,658,874			$ 980,000	$ 8	$ 979,992
Costs related to the follow-on public offering	(953)
Foreign currency translation	0
Stock-based compensation	271,844					271,844
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)