CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Net revenues:
Revenues	$ 98,701	$ 98,615	$ 202,020	$ 196,552
Cost of revenues:
Total cost of revenues	42,041	42,283	84,078	84,513
Gross profit	56,660	56,332	117,942	112,039
Operating expenses:
Research and development	15,180	15,985	31,465	31,670
Marketing and selling	26,129	27,759	51,007	53,891
General and administrative	12,721	14,041	26,509	27,996
Amortization of intangible assets	332	363	695	726
Restructuring costs, net	(269)	268	289	3,175
Total operating expenses	54,093	58,416	109,965	117,458
Operating income (loss)	2,567	(2,084)	7,977	(5,419)
Interest and other expense, net	(13,290)	(6,278)	(18,475)	(11,637)
(Loss) income before income taxes	(10,723)	(8,362)	(10,498)	(17,056)
Provision for income taxes	0	144	438	399
Net (loss) income	$ (10,723)	$ (8,506)	$ (10,936)	$ (17,455)
Net (loss) income per common share, basic and diluted	$ (0.25)	$ (0.20)	$ (0.26)	$ (0.42)
Weighted-average common shares outstanding - basic and diluted	42,560	41,587	42,305	41,496
Product [Member]
Net revenues:
Revenues	$ 50,326	$ 46,379	$ 104,722	$ 92,789
Cost of revenues:
Cost of revenues	28,058	26,347	55,658	52,642
Service [Member]
Net revenues:
Revenues	48,375	52,236	97,298	103,763
Cost of revenues:
Cost of revenues	12,195	13,986	24,682	27,971
Amortization of intangible assets [Member]
Cost of revenues:
Amortization of intangible assets	$ 1,788	$ 1,950	$ 3,738	$ 3,900