FINANCIAL INFORMATION Revenue, Initial Application Period Cumulative Effect Transition (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2018
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Accrued expenses and other current liabilities	$ 41,402		$ 37,547
Accounts receivable, net of allowances of $1,339 and $1,339 at March 31, 2019 and December 31, 2018, respectively	61,318		67,754
Contract assets	18,677		16,513
Inventory, Net	(34,328)		(32,956)
Other long-term assets	9,456		9,432
Assets	299,670		265,843
Deferred Revenue, Current	(87,927)		(85,662)
Deferred Revenue, Noncurrent	(13,361)		(13,939)
Liabilities	(466,757)		(432,504)
Accumulated deficit	(1,187,223)		(1,187,010)
Stockholders' Equity Attributable to Parent	(167,087)		(166,661)
Revenues	$ 103,319	$ 97,937
Difference between Revenue Guidance in Effect before and after Topic 606 [Member]
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Inventory, Net			$ (5,716)