Condensed Consolidated Statements of Redeemable Convertible Preferred Stock and Stockholders' Deficit (Unaudited) - USD ($) $ in Thousands	Total	Redeemable Convertible Preferred Stock	Common Stock	Additional Paid-In Capital	Accumulated Deficit	Accumulated Other Comprehensive Income (Loss)
Beginning balance at Dec. 31, 2017	$ (1,979,438)			$ 55,568	$ (2,033,995)	$ (1,011)
Beginning balance, shares at Dec. 31, 2017		199,815,000
Beginning balance at Dec. 31, 2017		$ 4,284,049
Beginning balance, shares at Dec. 31, 2017			19,916,000
Issuance of Series H redeemable convertible preferred stock, net of issuance cost		$ 54,193
Issuance of Series H Redeemable Convertible Preferred Stock, net of issuance cost, shares		1,364,000
Issuance of common stock upon exercise of stock options	1,169			1,169
Issuance of common stock upon exercise of stock options, shares			335,000
Vesting of early exercised stock options	13			13
Stock-based compensation	1,996			1,996
Other comprehensive income (loss)	(1,013)					(1,013)
Net loss	(234,339)				(234,339)
Ending balance at Mar. 31, 2018	(2,211,612)			58,746	(2,268,334)	(2,024)
Ending balance, shares at Mar. 31, 2018		201,179,000
Ending balance at Mar. 31, 2018		$ 4,338,242
Ending balance, shares at Mar. 31, 2018			20,251,000
Beginning balance at Dec. 31, 2018	(2,871,281)			73,916	(2,945,330)	133
Beginning balance, shares at Dec. 31, 2018		219,175,709
Beginning balance at Dec. 31, 2018	$ 5,152,047	$ 5,152,047
Beginning balance, shares at Dec. 31, 2018	22,438,472		22,438,000
Issuance of common stock upon exercise of stock options	$ 1,599			1,599
Issuance of common stock upon exercise of stock options, shares			7,121,000
Issuance of common stock upon settlement of RSUs, shares			17,688,000
Shares withheld related to net share settlement	(785,004)			(785,004)
Shares withheld related to net share settlement, shares			(11,415,000)
Vesting of early exercised stock options	2			2
Stock-based compensation	859,486			859,486
Other comprehensive income (loss)	2,053					2,053
Net loss	(1,138,473)				(1,138,473)
Ending balance at Mar. 31, 2019	(3,931,618)			$ 149,999	$ (4,083,803)	$ 2,186
Ending balance, shares at Mar. 31, 2019		219,175,709
Ending balance at Mar. 31, 2019	$ 5,152,047	$ 5,152,047
Ending balance, shares at Mar. 31, 2019	35,831,684		35,832,000