QUARTERLY RESULTS (UNAUDITED) (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2021	Sep. 30, 2021	Jun. 30, 2021	Mar. 31, 2021	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Net revenues	$ 119,064	$ 101,640	$ 94,876	$ 94,364	$ 104,301	$ 90,431	$ 79,281	$ 86,453	$ 409,944	$ 360,466	$ 411,788
Amortization of intangible assets									0	0	3,738
Cost of services	40,717	35,737	34,738	32,948	38,951	32,174	27,719	33,302
Gross profit	78,347	65,903	60,138	61,416	65,350	58,257	51,562	53,151	265,804	228,320	249,075
Operating expenses:
Research and development	16,920	17,129	16,093	15,417	14,902	13,623	13,068	15,425	65,559	57,018	62,343
Marketing and selling	28,983	24,413	21,354	20,744	22,660	19,998	19,690	25,289	95,494	87,637	99,944
General and administrative	15,158	14,901	13,678	13,635	12,908	10,796	10,604	12,744	57,372	47,052	53,362
Amortization of intangible assets									0	0	694
Restructuring costs (recoveries), net	115	(88)	15	1,074	4,038	723	140	145	1,116	5,046	629
Total operating expenses	61,176	56,355	51,140	50,870	54,508	45,140	43,502	53,603	219,541	196,753	216,972
Operating income (loss)	17,171	9,548	8,998	10,546	10,842	13,117	8,060	(452)	46,263	31,567	32,103
Other income (expense), net	389	7,864	150	(3,555)	636	143	118	(28)
Income (Loss) from Continuing Operations before Income Taxes, Noncontrolling Interest	15,951	15,766	7,365	4,873	6,913	8,694	2,562	(5,735)	43,955	12,434	2,525
Provision for (benefit from) income taxes	735	991	359	482	(174)	707	717	122	2,567	1,372	(5,076)
Net income (loss)	$ 15,216	$ 14,775	$ 7,006	$ 4,391	$ 7,087	$ 7,987	$ 1,845	$ (5,857)	$ 41,388	$ 11,062	$ 7,601
Earnings Per Share, Basic	$ 0.34	$ 0.32	$ 0.15	$ 0.10	$ 0.16	$ 0.18	$ 0.04	$ (0.14)	$ 0.92	$ 0.25	$ 0.18
Earnings Per Share, Diluted	$ 0.33	$ 0.32	$ 0.15	$ 0.10	$ 0.16	$ 0.18	$ 0.04	$ (0.13)	$ 0.89	$ 0.25	$ 0.17
Weighted-average common shares outstanding - basic	45,061	45,564	45,211	44,559	44,288	44,019	43,719	43,254	45,101	43,822	42,649
Weighted-average common shares outstanding - diluted	45,773	46,428	46,550	46,204	45,541	44,758	44,180	44,101	46,303	44,878	43,495