CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Net revenues:
Revenues	$ 93,461	$ 104,046	$ 295,481	$ 300,598
Cost of revenues:
Total cost of revenues	35,603	43,435	119,681	127,948
Gross profit	57,858	60,611	175,800	172,650
Operating expenses:
Research and development	14,860	15,873	46,325	47,543
Marketing and selling	22,334	23,461	73,341	77,352
General and administrative	12,034	13,660	38,543	41,656
Amortization of intangible assets	0	363	695	1,089
Restructuring costs, net	229	226	518	3,401
Total operating expenses	49,457	53,583	159,422	171,041
Operating income (loss)	8,401	7,028	16,378	1,609
Interest and other expense, net	(5,519)	(5,725)	(23,994)	(17,362)
Income (loss) before income taxes	2,882	1,303	(7,616)	(15,753)
Provision for (benefit from) income taxes	(283)	425	155	824
Net income (loss)	$ 3,165	$ 878	$ (7,771)	$ (16,577)
Net income (loss) per common share – basic and diluted	$ 0.07	$ 0.02	$ (0.18)	$ (0.40)
Weighted-average common shares outstanding – basic	42,913	41,792	42,510	41,596
Weighted-average common shares outstanding – diluted	43,674	42,226	42,510	41,596
Product [Member]
Net revenues:
Revenues	$ 42,911	$ 52,133	$ 147,633	$ 144,922
Cost of revenues:
Cost of revenues	23,877	27,042	79,535	79,684
Service [Member]
Net revenues:
Revenues	50,550	51,913	147,848	155,676
Cost of revenues:
Cost of revenues	11,726	14,443	36,408	42,414
Amortization of intangible assets [Member]
Cost of revenues:
Amortization of intangible assets	$ 0	$ 1,950	$ 3,738	$ 5,850