QUARTERLY RESULTS (UNAUDITED) (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Net revenues	$ 115,295	$ 119,019	$ 134,069	$ 143,547	$ 138,806	$ 137,436	$ 109,767	$ 119,586	$ 511,930	$ 505,595	$ 530,251
Cost of revenues	43,876	41,678	44,320	41,533	54,912	47,672	43,306	47,492
Cost of products									111,579	131,881	143,765
Cost of services									59,828	61,501	60,656
Amortization of intangible assets	1,950	1,950	1,950	1,950	1,950	1,950	163	0	7,800	4,063	50
Gross profit	69,469	75,391	87,799	100,064	81,944	87,814	66,298	72,094	332,723	308,150	325,780
Operating expenses:
Research and development	18,773	19,953	21,433	21,405	24,190	25,225	23,310	23,173	81,564	95,898	90,390
Marketing and selling	21,311	27,231	30,177	31,619	30,091	31,564	32,811	28,045	110,338	122,511	133,049
General and administrative	13,112	13,822	16,818	17,719	21,463	15,834	17,425	19,387	61,471	74,109	81,181
Amortization of intangible assets	363	567	782	786	786	786	408	374	2,498	2,354	1,626
Restructuring costs (recoveries), net	4,959	5,314	(213)	2,777	5,766	0	539	0	12,837	6,305	(165)
Total operating expenses	58,518	66,887	68,997	74,306	82,296	73,409	74,493	70,979	268,708	301,177	306,081
Operating income (loss)	10,951	8,504	18,802	25,758	(352)	14,405	(8,195)	1,115	64,015	6,973	19,699
Other income (expense), net	(4,622)	(4,707)	(5,159)	(4,183)	(1,727)	(2,519)	(1,439)	(723)	232	(175)	(1,138)
Income (loss) before income taxes	6,329	3,797	13,643	21,575	(2,079)	11,886	(9,634)	392	45,344	565	16,916
Provision for (benefit from) income taxes	1,108	(5,321)	703	635	2,306	768	(5,550)	561	(2,875)	(1,915)	2,188
Net income (loss)	$ 5,221	$ 9,118	$ 12,940	$ 20,940	$ (4,385)	$ 11,118	$ (4,084)	$ (169)	$ 48,219	$ 2,480	$ 14,728
Net income (loss) per common share - basic and diluted	$ 0.13	$ 0.23	$ 0.33	$ 0.53	$ (0.11)	$ 0.28	$ (0.10)	$ 0.00	$ 1.20	$ 0.06	$ 0.38
Weighted-average common shares outstanding - basic	40,637	40,194	39,678	39,566	39,439	39,231	39,635	39,387	40,021	39,423	39,147
Weighted-average common shares outstanding - diluted	40,746	40,476	39,734	39,640	39,439	39,750	39,635	39,387	40,176	40,380	39,267