BUSINESS SEGMENTS (Details) - USD ($)	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016		Dec. 31, 2015		Dec. 31, 2014
Segment reporting information
Revenue, net	$ 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 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
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
Operating expenses	98,346,000	84,763,000	81,831,000	59,494,000	86,198,000	75,822,000	71,575,000	71,593,000	324,434,000		305,188,000		267,136,000
Interest and other income (expense), net									13,630,000		3,649,000		1,282,000
Pre-tax income (loss)	3,880,000	(3,935,000)	(1,458,000)	22,058,000	(2,016,000)	(2,632,000)	3,275,000	4,488,000	20,545,000		3,115,000		13,205,000
Provision (benefit) for income taxes	1,119,000	(543,000)	(243,000)	8,964,000	(1,879,000)	(15,000)	1,849,000	1,940,000	9,297,000		1,895,000		4,404,000
Consolidated net income	2,761,000	(3,392,000)	(1,215,000)	13,094,000	(137,000)	(2,617,000)	1,426,000	2,548,000	11,248,000		1,220,000		8,801,000
Depreciation and amortization									27,283,000		23,516,000		17,961,000
Retail
Segment reporting information
Revenue, net									1,784,782,000		1,655,908,000		1,497,103,000
Total cost of goods sold									1,458,411,000		1,353,184,000		1,218,044,000
Gross profit									326,371,000		302,724,000		279,059,000
Operating expenses									307,669,000		296,281,000		267,136,000
Interest and other income (expense), net									13,630,000		3,649,000		1,282,000
Pre-tax income (loss)									32,332,000		10,092,000		13,205,000
Provision (benefit) for income taxes									13,797,000		3,448,000		4,404,000
Consolidated net income									18,535,000		6,644,000		8,801,000
Depreciation and amortization									26,900,000		23,600,000		18,100,000
Direct
Segment reporting information
Revenue, net	25,677,000	24,620,000	24,630,000	26,651,000	33,599,000	33,621,000	34,428,000	36,135,000	101,578,000		137,783,000		147,460,000
Total cost of goods sold	$ 23,812,000	$ 23,955,000	$ 23,098,000	$ 25,406,000	$ 32,326,000	$ 31,989,000	$ 31,235,000	$ 32,527,000	96,271,000	[1]	128,077,000	[1]	129,253,000	[1]
Gross profit									5,307,000		9,706,000		18,207,000
Partner
Segment reporting information
Revenue, net									1,683,204,000		1,518,125,000		1,349,643,000
Total cost of goods sold									1,362,140,000		1,225,107,000		1,088,791,000
Gross profit									321,064,000		293,018,000		260,852,000
Other
Segment reporting information
Revenue, net									15,181,000		1,930,000		0
Total cost of goods sold									10,203,000		0		0
Gross profit									4,978,000		1,930,000		0
Operating expenses									16,765,000		8,907,000		0
Interest and other income (expense), net									0		0		0
Pre-tax income (loss)									(11,787,000)		(6,977,000)		0
Provision (benefit) for income taxes									(4,500,000)		(1,553,000)		0
Consolidated net income									(7,287,000)		(5,424,000)		0
Depreciation and amortization									4,400,000		1,500,000		0
Inter-segment
Segment reporting information
Revenue, net									0
Interest and other income (expense), net									$ 594,000		$ 158,000		$ 0

[1] (1) Includes stock-based compensation as follows (Note 15): Cost of goods sold — direct $266 $179 $181 Sales and marketing 249 217 336 Technology 777 646 751 General and administrative 3,599 2,484 2,767 Total $4,891 $3,526 $4,035