ACCOUNTING POLICIES (Details 5) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017 USD ($)	Sep. 30, 2017 USD ($)	Jun. 30, 2017 USD ($)	Mar. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)	Sep. 30, 2016 USD ($)	Jun. 30, 2016 USD ($)	Mar. 31, 2016 USD ($)	Dec. 31, 2017 USD ($) segment	Dec. 31, 2016 USD ($)	Dec. 31, 2015 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
Club O loyalty program
Loyalty program expiration period									90 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	$ 17,400				$ 18,200				$ 17,400	$ 18,200
Credit card chargeback allowance
Credit card chargeback allowance	311				431				311	431
Cost of goods sold
Total net revenue	456,290	$ 424,007	$ 432,024	$ 432,435	526,182	$ 441,564	$ 418,540	$ 413,677	$ 1,744,756	$ 1,799,963	$ 1,657,838
Total revenue, net (as a percent)									100.00%	100.00%	100.00%
Cost of goods sold
Product costs and other cost of goods sold									$ 1,328,749	$ 1,391,736	$ 1,279,766
Fulfillment and related costs									75,456	76,878	73,418
Total cost of goods sold	370,492	340,332	347,853	345,528	428,178	361,848	342,218	336,370	$ 1,404,205	$ 1,468,614	$ 1,353,184
Product costs and other cost of goods sold (as a percent)									76.00%	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)									80.00%	82.00%	82.00%
Gross profit	85,798	$ 83,675	$ 84,171	$ 86,907	98,004	$ 79,716	$ 76,322	$ 77,307	$ 340,551	$ 331,349	$ 304,654
Gross profit (as a percent)									20.00%	18.00%	18.00%
Advertising expense
Advertising expense									$ 164,600	$ 135,100	$ 115,000
Prepaid advertising	987				$ 843				987	$ 843
Accrued liability for self-funded health insurance	$ 1,000								$ 1,000