UNAUDITED SELECTED QUARTERLY FINANCIAL DATA (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Revenue:
Product	$ 38,920	$ 36,130	$ 30,751	$ 20,480	$ 31,149	$ 30,776	$ 33,721	$ 24,861	$ 126,281	$ 120,507	$ 97,564
Software subscription and services	7,306	6,650	6,085	5,337	5,031	4,550	3,833	3,371	25,378	16,785	9,571
Total revenue	46,226	42,780	36,836	25,817	36,180	35,326	37,554	28,232	151,659	137,292	107,135
Cost of revenue
Product	12,362	11,707	9,619	6,808	10,159	9,764	10,560	7,882	40,496	38,365	31,431
Software subscription and services	2,857	2,686	2,526	1,828	1,717	1,678	1,639	1,366	9,897	6,400	4,250
Total cost of revenue	15,219	14,393	12,145	8,636	11,876	11,442	12,199	9,248	50,393	44,765	35,681
Gross profit	31,007	28,387	24,691	17,181	24,304	23,884	25,355	18,984	101,266	92,527	71,454
Operating expenses:
Research and development	10,433	10,098	8,883	7,510	7,031	7,544	6,833	6,138	36,924	27,546	25,742
Sales and marketing	21,409	22,083	20,804	18,770	18,728	18,056	19,011	16,569	83,066	72,364	57,773
General and administrative	6,638	7,212	6,206	6,247	5,984	5,224	5,135	4,837	26,303	21,180	17,689
Operating loss	(7,473)	(11,006)	(11,202)	(15,346)	(7,439)	(6,940)	(5,624)	(8,560)	(45,027)	(28,563)	(29,750)
Interest income	54	21	19	14	18	10	8	1	108	37	15
Interest expense	(142)	(140)	(173)	(754)	(461)	(458)	(459)	(465)	(1,209)	(1,843)	(604)
Other income (expense), net	72	59	19	135	101	95	(58)	117	285	255	(2,462)
Loss before income taxes	(7,489)	(11,066)	(11,337)	(15,951)	(7,781)	(7,293)	(6,133)	(8,907)	(45,843)	(30,114)	(32,801)
Income tax provision	70	(215)	(99)	(108)	(205)	(81)	(135)	(20)	(352)	(441)	(426)
Net loss	$ (7,419)	$ (11,281)	$ (11,436)	$ (16,059)	$ (7,986)	$ (7,374)	$ (6,268)	$ (8,927)	$ (46,195)	$ (30,555)	$ (33,227)