Description of Business and Basis of Presentation - Schedule of Unaudited Pro forma Condensed Consolidated Balance Sheet (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018	Mar. 31, 2018	Dec. 31, 2017
Assets
Total current assets	$ 1,380,412	$ 2,320,442
Total noncurrent assets	1,860,495
Total assets	3,240,907	3,760,043
Liabilities, Redeemable Convertible Preferred Stock and Stockholders’ Deficit
Total liabilities	2,020,478	1,479,277
Redeemable convertible preferred stock, $0.00001 par value, 227,328,900 shares authorized as of March 31, 2019 and December 31, 2018; 219,175,709 issued and outstanding as of March 31, 2019 and December 31, 2018	5,152,047	5,152,047
Stockholders’ deficit
Additional paid-in capital	149,999	73,916
Accumulated other comprehensive income	2,186	133
Accumulated deficit	(4,083,803)	(2,945,330)
Total stockholders’ equity (deficit)	(3,931,618)	(2,871,281)	$ (2,211,612)	$ (1,979,438)
Total liabilities, redeemable convertible preferred stock and stockholders’ equity (deficit)	3,240,907	3,760,043
Proforma Adjustments
Assets
Total current assets	2,489,638
Total noncurrent assets	(7,690)
Total assets	2,481,948
Liabilities, Redeemable Convertible Preferred Stock and Stockholders’ Deficit
Total liabilities	(2,240)
Stockholders’ deficit
Additional paid-in capital	7,636,233
Total stockholders’ equity (deficit)	7,636,235
Total liabilities, redeemable convertible preferred stock and stockholders’ equity (deficit)	2,481,948
Proforma
Assets
Total current assets	3,870,050
Total noncurrent assets	1,852,805
Total assets	5,722,855
Liabilities, Redeemable Convertible Preferred Stock and Stockholders’ Deficit
Total liabilities	2,018,238
Stockholders’ deficit
Additional paid-in capital	7,786,232
Accumulated other comprehensive income	2,186
Accumulated deficit	(4,083,803)
Total stockholders’ equity (deficit)	3,704,617
Total liabilities, redeemable convertible preferred stock and stockholders’ equity (deficit)	5,722,855
Redeemable Convertible Preferred Stock
Liabilities, Redeemable Convertible Preferred Stock and Stockholders’ Deficit
Redeemable convertible preferred stock, $0.00001 par value, 227,328,900 shares authorized as of March 31, 2019 and December 31, 2018; 219,175,709 issued and outstanding as of March 31, 2019 and December 31, 2018	5,152,047	$ 5,152,047	$ 4,338,242	$ 4,284,049
Redeemable Convertible Preferred Stock | Proforma Adjustments
Liabilities, Redeemable Convertible Preferred Stock and Stockholders’ Deficit
Redeemable convertible preferred stock, $0.00001 par value, 227,328,900 shares authorized as of March 31, 2019 and December 31, 2018; 219,175,709 issued and outstanding as of March 31, 2019 and December 31, 2018	(5,152,047)
Class A Common Stock | Proforma Adjustments
Stockholders’ deficit
Class A common stock	2
Class A Common Stock | Proforma
Stockholders’ deficit
Class A common stock	$ 2