ACCOUNTING POLICIES - Schedule of Costs of Goods Sold (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Revenue recognition
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%
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
Cost of goods sold
Total net revenue	$ 370,881	$ 347,099	$ 373,709	$ 367,729	$ 452,548	$ 440,580	$ 483,133	$ 445,331	$ 1,459,418	$ 1,821,592	$ 1,744,756
Total revenue, net (as a percent)									100.00%	100.00%	100.00%
Cost of goods sold
Product costs and other cost of goods sold									$ 1,100,351	$ 1,390,750	$ 1,328,749
Fulfillment and related costs									65,974	76,934	75,456
Total cost of goods sold	294,359	277,551	299,810	294,605	370,968	353,864	391,390	351,462	$ 1,166,325	$ 1,467,684	$ 1,404,205
Product costs and other cost of goods sold (as a percent)									75.00%	76.00%	76.00%
Fulfillment and related costs (as a percent)									5.00%	4.00%	4.00%
Total cost of goods sold (as a percent)									80.00%	81.00%	80.00%
Gross profit	$ 76,522	$ 69,548	$ 73,899	$ 73,124	$ 81,580	$ 86,716	$ 91,743	$ 93,869	$ 293,093	$ 353,908	$ 340,551
Gross profit (as a percent)									20.00%	19.00%	20.00%
Advertising Revenue as a Percentage of Total Revenue									2.00%	2.00%	2.00%