ACCOUNTING POLICIES (Details 4)	3 Months Ended								12 Months Ended
	Dec. 31, 2016 USD ($)	Sep. 30, 2016 USD ($)	Jun. 30, 2016 USD ($)	Mar. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)	Sep. 30, 2015 USD ($)	Jun. 30, 2015 USD ($)	Mar. 31, 2015 USD ($)	Dec. 31, 2016 USD ($) segment	Dec. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)
Revenue recognition
Number of principal segments | segment									2
Product delivery period from date of shipment, minimum									1 day
Product delivery period from date of shipment, maximum									8 days
Co-branded credit card program
Maximum revenue from co-branded credit card program as a percentage of total net revenues									1.00%	1.00%	1.00%
Deferred revenue
Likelihood of gift card redemption to be remote, period									36 months
Sales returns allowance
Sales return period for which full refund will be granted									30 days
Sales return period for which reduced refund will be granted									30 days
Sales return received at returns processing facility for which reduced refund will be granted, period									45 days
Allowance for sales returns	$ 18,200,000				$ 17,900,000				$ 18,200,000	$ 17,900,000
Credit card chargeback allowance
Credit card chargeback allowance	431,000				240,000				431,000	240,000
Cost of goods sold
Total net revenue	526,182,000	$ 441,564,000	$ 418,540,000	$ 413,677,000	480,270,000	$ 391,211,000	$ 388,013,000	$ 398,344,000	$ 1,799,963,000	$ 1,657,838,000	$ 1,497,103,000
Total revenue, net (as a percent)									100.00%	100.00%	100.00%
Cost of goods sold
Product costs and other cost of goods sold									$ 1,391,736,000	$ 1,279,766,000	$ 1,152,489,000
Fulfillment and related costs									76,878,000	73,418,000	65,555,000
Total cost of goods sold	428,178,000	361,848,000	342,218,000	336,370,000	397,161,000	318,760,000	314,356,000	322,907,000	$ 1,468,614,000	$ 1,353,184,000	$ 1,218,044,000
Product costs and other cost of goods sold (as a percent)									77.00%	77.00%	77.00%
Fulfillment and related costs (as a percent)									4.00%	4.00%	4.00%
Total cost of goods sold (as a percent)									82.00%	82.00%	81.00%
Gross profit	98,004,000	$ 79,716,000	$ 76,322,000	$ 77,307,000	83,109,000	$ 72,451,000	$ 73,657,000	$ 75,437,000	$ 331,349,000	$ 304,654,000	$ 279,059,000
Gross profit (as a percent)									18.00%	18.00%	19.00%
Advertising expense
Advertising expense									$ 135,100,000	$ 115,000,000	$ 99,600,000
Prepaid advertising	$ 843,000				$ 1,244,000				843,000	1,244,000
Gain (Loss) on Investment in Precious Metals									$ 201,000	$ (1,183,000)	$ (1,269,000)