CONSOLIDATED AND CONDENSED STATEMENTS OF OPERATIONS - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Income Statement [Abstract]
Net revenue	$ 2,305,487	$ 1,705,645	$ 6,593,567	$ 4,765,170
Cost of goods sold	1,765,566	1,312,875	5,023,590	3,663,569
Gross profit	539,921	392,770	1,569,977	1,101,601
Operating expenses:
Customer service and merchant fees	91,255	66,664	256,230	182,340
Advertising	281,846	202,587	784,981	541,815
Selling, operations, technology, general and administrative	426,529	268,785	1,153,286	721,120
Total operating expenses	799,630	538,036	2,194,497	1,445,275
Loss from operations	(259,709)	(145,266)	(624,520)	(343,674)
Interest expense, net	(14,432)	(7,066)	(33,922)	(18,269)
Other income, net	2,182	1,054	5,582	2,661
Loss before income taxes	(271,959)	(151,278)	(652,860)	(359,282)
Provision for income taxes	76	448	1,502	953
Net loss	$ (272,035)	$ (151,726)	$ (654,362)	$ (360,235)
Net loss per share, basic and diluted (in dollars per share)	$ (2.94)	$ (1.69)	$ (7.13)	$ (4.04)
Weighted average number of common stock outstanding used in computing per share amounts, basic and diluted (in shares)	92,540	89,792	91,820	89,144