RECLASSIFICATIONS (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2019	Mar. 31, 2018	Mar. 31, 2017
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Total revenue	$ 93,767	$ 89,912	$ 85,682	$ 83,225	$ 79,344	$ 75,575	$ 72,483	$ 69,098	$ 66,489	$ 63,676	$ 63,183	$ 60,041	$ 352,586	$ 296,500	$ 253,388
Research and development	18,064	16,886	14,064	13,050	10,427	8,903	8,714	8,361	7,520	7,462	6,835	7,181	62,063	36,405	28,999
Sales and marketing	49,525	46,276	41,680	40,495	40,422	36,382	28,680	28,460	27,351	25,770	24,328	21,444	177,976	133,945	98,893
General and administrative	20,365	18,038	20,326	14,833	12,566	13,489	13,105	12,691	13,037	10,622	9,105	9,111	73,563	51,851	41,875
Impairment of goodwill, intangible assets and equipment					0	9,469	0	0					0	9,469	0
Loss from operations	(28,780)	(24,238)	(21,987)	(15,983)	(13,730)	(18,247)	(4,462)	(5,457)	(3,685)	(1,703)	(379)	(901)	(90,988)	(41,896)	(6,669)
Pre-Reclassification
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Total revenue	93,767	89,912	85,682	83,225	79,344	75,575	72,483	69,098	66,489	63,676	63,183	60,041	352,586	296,500	253,388
Research and development	17,815	16,876	13,933	13,110	10,016	8,527	8,311	7,943	7,142	7,094	6,505	6,710	61,734	34,797	27,452
Sales and marketing	64,610	60,717	55,930	53,305	52,940	48,830	41,163	41,110	38,228	35,667	33,691	31,691	234,562	184,044	139,277
General and administrative	16,666	14,196	16,543	11,433	10,340	10,003	9,616	8,956	9,814	7,852	6,747	6,801	58,838	38,915	31,214
Impairment of goodwill, intangible assets and equipment					0	9,469	0	0						9,469
Loss from operations	(28,780)	(24,238)	(21,987)	(15,983)	(13,730)	(18,247)	(4,462)	(5,457)	(3,685)	(1,703)	(379)	(901)	(90,988)	(41,896)	(6,669)
Reclassifications
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Total revenue	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0
Research and development	249	10	131	(60)	411	376	403	418	378	368	330	471	330	1,608	1,547
Sales and marketing	(15,085)	(14,441)	(14,250)	(12,810)	(12,518)	(12,448)	(12,483)	(12,650)	(10,877)	(9,897)	(9,363)	(10,247)	(56,586)	(50,099)	(40,384)
General and administrative	3,699	3,842	3,783	3,400	2,226	3,486	3,489	3,735	3,223	2,770	2,358	2,310	14,724	12,936	10,661
Loss from operations	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0
Service
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Total revenue													334,438	280,430	235,816
Cost of revenue	28,809	27,632	26,202	24,549	23,833	20,904	21,348	20,159	18,079	17,285	17,512	17,701	107,192	86,244	70,576
Service \| Pre-Reclassification
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Cost of revenue	17,672	17,043	15,866	15,079	13,952	12,318	12,757	11,662	10,803	10,526	10,837	10,235	65,660	50,689	42,400
Service \| Reclassifications
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Cost of revenue	11,137	10,589	10,336	9,470	9,881	8,586	8,591	8,497	7,276	6,759	6,675	7,466	41,532	35,555	28,176
Product
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Total revenue													18,148	16,070	17,572
Cost of revenue	5,784	5,318	5,397	6,281	5,826	4,675	5,098	4,884	4,187	4,240	5,782	5,505	22,780	20,482	19,714
Product \| Pre-Reclassification
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Cost of revenue	5,784	5,318	5,397	6,281	5,826	4,675	5,098	4,884	4,187	4,240	5,782	5,505	22,780	20,482	19,714
Product \| Reclassifications
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Cost of revenue	$ 0	$ 0	$ 0	$ 0	$ 0	$ 0	$ 0	$ 0	$ 0	$ 0	$ 0	$ 0	$ 0	$ 0	$ 0

Amount of write-down of assets recognized in the income statement. Includes, but is not limited to, losses from tangible assets, intangible assets and goodwill.

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