SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES Revenue, Initial Application Period Cumulative Effect Transition (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Net revenues	$ 112,684	$ 104,046	$ 98,615	$ 97,937	$ 107,258	$ 105,265	$ 102,373	$ 104,107	$ 413,282	$ 419,003	$ 511,930
Accounts Receivable, Net, Current	67,754				40,134				67,754	40,134
Contract with Customer, Asset, Gross	16,513				0				16,513	0
Inventory, Net	(32,956)				(38,421)				(32,956)	(38,421)
Other Assets, Noncurrent	9,432				10,811				9,432	10,811
Assets	265,843				234,684				265,843	234,684
Accrued Liabilities, Current	37,547				31,549				37,547	31,549
Deferred Revenue, Current	(85,662)				(121,184)				(85,662)	(121,184)
Deferred Revenue, Noncurrent	(13,939)				(73,429)				(13,939)	(73,429)
Liabilities	(432,504)				(503,254)				(432,504)	(503,254)
Retained Earnings (Accumulated Deficit)	(1,187,010)				(1,284,703)				(1,187,010)	(1,284,703)
Stockholders' Equity Attributable to Parent	(166,661)				(268,570)				(166,661)	(268,570)
Cost of Revenue									174,118	176,887	179,207
Gross Profit	66,514	60,611	56,332	55,707	58,446	60,358	59,753	63,559	239,164	242,116	332,723
Marketing and selling	23,921	23,461	27,759	26,132	25,776	25,652	29,018	25,811	101,273	106,257	110,338
Income (Loss) from Continuing Operations before Income Taxes, Noncontrolling Interest									(9,403)	(13,422)	45,344
Net (loss) income	$ 5,903	$ 878	$ (8,506)	$ (8,949)	$ (881)	$ 72	$ (10,831)	$ (1,915)	$ (10,674)	(13,555)	$ 48,219
Earnings Per Share, Basic and Diluted	$ 0.14	$ 0.02	$ (0.20)	$ (0.22)	$ (0.02)	$ 0.00	$ (0.26)	$ (0.05)	$ (0.0026)
Accounting Standards Update 2014-09 [Member]
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Net revenues									$ (515)
Accounts Receivable, Net, Current	$ (19,703)				$ 61,222				(19,703)	61,222
Contract with Customer, Asset, Gross	(16,513)				6,579				(16,513)	6,579
Inventory, Net	(10,418)				(32,705)				(10,418)	(32,705)
Other Assets, Noncurrent	(900)				11,676				(900)	11,676
Assets	(26,698)				257,500				(26,698)	257,500
Accrued Liabilities, Current	(9,003)				42,688				(9,003)	42,688
Deferred Revenue, Current	(32,223)				(79,573)				(32,223)	(79,573)
Deferred Revenue, Noncurrent	(54,246)				(18,350)				(54,246)	(18,350)
Liabilities	(77,466)				(417,703)				(77,466)	(417,703)
Retained Earnings (Accumulated Deficit)	(104,164)				(1,176,336)				(104,164)	(1,176,336)
Stockholders' Equity Attributable to Parent	(104,164)				(160,203)				(104,164)	(160,203)
Cost of Revenue									(4,718)
Gross Profit									4,203
Marketing and selling									51
Income (Loss) from Continuing Operations before Income Taxes, Noncontrolling Interest									4,203
Net (loss) income									$ 4,203
Earnings Per Share, Basic and Diluted									$ 0.0010
Calculated under Revenue Guidance in Effect before Topic 606 [Member]
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Net revenues									$ 412,767
Accounts Receivable, Net, Current	48,051								48,051
Contract with Customer, Asset, Gross	0								0
Inventory, Net	(43,374)								(43,374)
Other Assets, Noncurrent	8,532								8,532
Assets	239,145								239,145
Accrued Liabilities, Current	28,544								28,544
Deferred Revenue, Current	(117,885)								(117,885)
Deferred Revenue, Noncurrent	(68,185)								(68,185)
Liabilities	(509,970)								(509,970)
Retained Earnings (Accumulated Deficit)	(1,291,174)								(1,291,174)
Stockholders' Equity Attributable to Parent	$ (270,825)								(270,825)
Cost of Revenue									169,400
Gross Profit									243,367
Marketing and selling									101,324
Income (Loss) from Continuing Operations before Income Taxes, Noncontrolling Interest									(5,200)
Net (loss) income									$ (6,471)
Earnings Per Share, Basic and Diluted									$ (0.0016)
Difference between Revenue Guidance in Effect before and after Topic 606 [Member]
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Accounts Receivable, Net, Current					21,088					21,088
Contract with Customer, Asset, Gross					6,579					6,579
Inventory, Net					(5,716)					(5,716)
Other Assets, Noncurrent					865					865
Assets					22,816					22,816
Accrued Liabilities, Current					11,139					11,139
Deferred Revenue, Current					(41,611)					(41,611)
Deferred Revenue, Noncurrent					(55,079)					(55,079)
Liabilities					(85,551)					(85,551)
Retained Earnings (Accumulated Deficit)					108,367					108,367
Stockholders' Equity Attributable to Parent					$ 108,367					$ 108,367