CONSOLIDATED AND CONDENSED STATEMENTS OF OPERATIONS - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Income Statement [Abstract]
Net revenue	$ 1,198,198	$ 861,525	$ 3,281,879	$ 2,395,801
Cost of goods sold	917,889	659,864	2,495,221	1,826,570
Gross profit	280,309	201,661	786,658	569,231
Operating expenses:
Customer service and merchant fees	42,949	33,872	117,132	91,286
Advertising	141,714	101,333	384,220	293,436
Merchandising, marketing and sales	56,934	48,550	160,033	129,679
Operations, technology, general and administrative	112,669	79,526	292,988	207,289
Total operating expenses	354,266	263,281	954,373	721,690
Loss from operations	(73,957)	(61,620)	(167,715)	(152,459)
Interest (expense) income, net	(2,008)	(292)	(3,857)	791
Other (expense) income, net	(227)	889	400	1,804
Loss before income taxes	(76,192)	(61,023)	(171,172)	(149,864)
Provision for (benefit from) income taxes	237	(83)	671	555
Net loss	$ (76,429)	$ (60,940)	$ (171,843)	$ (150,419)
Net loss per share, basic and diluted (in dollars per share)	$ (0.88)	$ (0.72)	$ (1.98)	$ (1.77)
Weighted average number of common stock outstanding used in computing per share amounts, basic and diluted (in shares)	87,283	85,105	86,679	84,779