CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Net revenues:
Products	$ 411,788	$ 413,282	$ 419,003
Cost of revenues:
Products		55,560	56,481
Cost, Amortization		7,800	7,800
Total cost of revenues	162,713	174,118	176,887
Gross profit	249,075	239,164	242,116
Operating expenses:
Research and development	62,343	62,379	68,212
Marketing and selling	99,944	101,273	106,257
General and administrative	53,362	55,230	53,892
Amortization of intangible assets	694	1,450	1,450
Restructuring costs, net	629	5,148	7,059
Total operating expenses	216,972	225,480	236,870
Operating income	32,103	13,684	5,246
Interest income	36	195	535
Interest expense	(26,712)	(23,474)	(19,964)
Other income (expense), net	(2,902)	192	761
(Loss) income before income taxes	2,525	(9,403)	(13,422)
Provision for (benefit from) income taxes	(5,076)	1,271	133
Net (loss) income	$ 7,601	$ (10,674)	$ (13,555)
Earnings Per Share, Basic	$ 0.18	$ (0.26)	$ (0.33)
Earnings Per Share, Diluted	$ 0.17	$ (0.26)	$ (0.33)
Weighted-average common shares outstanding - basic	42,649	41,662	41,020
Weighted-average common shares outstanding - diluted	43,495	41,662	41,020
Product [Member]
Net revenues:
Products	$ 207,445	$ 205,107	$ 209,461
Cost of revenues:
Products	109,799	110,758	112,606
Service [Member]
Net revenues:
Products	204,343	$ 208,175	$ 209,542
Cost of revenues:
Products	49,176
Amortization of intangible assets [Member]
Cost of revenues:
Cost, Amortization	$ 3,738