Condensed Consolidated Statements of Shareholders' Equity - USD ($) $ in Thousands	Total	Class A Common Stock, Class B Common Stock and Class C Capital Stock	Additional Paid-In Capital	Accumulated Deficit	Accumulated Other Comprehensive Income
Beginning Balance at Dec. 31, 2018	$ 3,267,179	$ 21	$ 3,939,842	$ (671,779)	$ (905)
Beginning Balance (in shares) at Dec. 31, 2018		203,904,265
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common and capital stock upon exercise of stock options	32,997		32,997
Issuance of common and capital stock upon exercise of stock options (in shares)		1,543,850
Vesting of restricted stock units (in shares)		1,065,607
Shares and value of restricted stock units withheld for tax liability	(3)		(3)
Shares and value of restricted stock units withheld for tax liability (in shares)		(86)
Share-based compensation expense	115,634		115,634
Net loss	(139,502)			(139,502)
Other comprehensive income (loss)	1,801				1,801
Ending Balance at Jun. 30, 2019	3,278,106	$ 21	4,088,470	(811,281)	896
Ending Balance (in shares) at Jun. 30, 2019		206,513,636
Beginning Balance at Mar. 31, 2019	3,283,132	$ 21	4,022,218	(739,304)	197
Beginning Balance (in shares) at Mar. 31, 2019		205,130,332
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common and capital stock upon exercise of stock options	19,433		19,433
Issuance of common and capital stock upon exercise of stock options (in shares)		814,062
Vesting of restricted stock units (in shares)		569,260
Shares and value of restricted stock units withheld for tax liability	(1)		(1)
Shares and value of restricted stock units withheld for tax liability (in shares)		(18)
Share-based compensation expense	46,820		46,820
Net loss	(71,977)			(71,977)
Other comprehensive income (loss)	699				699
Ending Balance at Jun. 30, 2019	3,278,106	$ 21	4,088,470	(811,281)	896
Ending Balance (in shares) at Jun. 30, 2019		206,513,636
Beginning Balance at Dec. 31, 2019	3,435,421	$ 21	4,412,200	(977,140)	340
Beginning Balance (in shares) at Dec. 31, 2019		209,066,855
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common and capital stock upon exercise of stock options	$ 184,985	$ 1	184,984
Issuance of common and capital stock upon exercise of stock options (in shares)	6,324,858	6,324,858
Vesting of restricted stock units (in shares)		1,414,158
Shares and value of restricted stock units withheld for tax liability	$ 0		0
Shares and value of restricted stock units withheld for tax liability (in shares)		(6)
Share-based compensation expense	104,636		104,636
Issuance of Class C capital stock in connection with equity offering, net of issuance costs	411,523	$ 1	411,522
Issuance of Class C capital stock in connection with equity offering, net of issuance costs (in shares)		8,800,000
Equity component of issuance of 2025 Notes, net of issuance costs	154,813		154,813
Partial repurchase of 2021 Notes	(21,784)		(21,784)
Partial repurchase of 2021 Notes (in shares)		753,936
Partial unwind of capped call transactions (in shares)		(317,865)
Net loss	(247,721)			(247,721)
Other comprehensive income (loss)	1,185				1,185
Ending Balance at Jun. 30, 2020	4,023,058	$ 23	5,246,371	(1,224,861)	1,525
Ending Balance (in shares) at Jun. 30, 2020		226,041,936
Beginning Balance at Mar. 31, 2020	3,415,761	$ 22	4,551,866	(1,140,413)	4,286
Beginning Balance (in shares) at Mar. 31, 2020		212,913,139
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common and capital stock upon exercise of stock options	92,783		92,783
Issuance of common and capital stock upon exercise of stock options (in shares)		3,117,483
Vesting of restricted stock units (in shares)		775,249
Shares and value of restricted stock units withheld for tax liability (in shares)		(6)
Share-based compensation expense	57,171		57,171
Issuance of Class C capital stock in connection with equity offering, net of issuance costs	411,523	$ 1	411,522
Issuance of Class C capital stock in connection with equity offering, net of issuance costs (in shares)		8,800,000
Equity component of issuance of 2025 Notes, net of issuance costs	154,813		154,813
Partial repurchase of 2021 Notes	(21,784)		(21,784)
Partial repurchase of 2021 Notes (in shares)		753,936
Partial unwind of capped call transactions (in shares)		(317,865)
Net loss	(84,448)			(84,448)
Other comprehensive income (loss)	(2,761)				(2,761)
Ending Balance at Jun. 30, 2020	$ 4,023,058	$ 23	$ 5,246,371	$ (1,224,861)	$ 1,525
Ending Balance (in shares) at Jun. 30, 2020		226,041,936