Consolidated Quarterly Financial Data (Unaudited) (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended								12 Months Ended
	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, 2018	Mar. 31, 2017	Mar. 31, 2016
Quarterly Financial Data Details
Service revenue	$ 75,325	$ 71,891	$ 68,123	$ 65,091	$ 62,654	$ 60,149	$ 57,717	$ 55,296	$ 280,430	$ 235,816	$ 192,241
Product revenue	4,019	3,684	4,360	4,007	3,834	3,527	5,466	4,745	16,070	17,572	17,095
Total revenue	79,344	75,575	72,483	69,098	66,488	63,676	63,183	60,041	296,500	253,388	209,336
Operating expenses:
Cost of service revenue	13,952	12,318	12,757	11,662	10,803	10,525	10,837	10,235	50,689	42,400	37,078
Cost of product revenue	5,826	4,675	5,098	4,884	4,187	4,240	5,782	5,505	20,482	19,714	20,168
Research and development	10,016	8,527	8,311	7,943	7,142	7,095	6,505	6,710	34,797	27,452	24,040
Sales and marketing	52,940	48,830	41,163	41,110	38,228	35,667	33,691	31,691	184,044	139,277	109,379
General and administrative	10,340	10,003	9,616	8,956	9,814	7,852	6,747	6,801	38,915	31,214	25,745
Impairment of goodwill, intangible assets and equipment	0	9,469	0	0	0	0	0	0	9,469	0	0
Total operating expenses	93,074	93,822	76,945	74,555	70,174	65,379	63,562	60,942	338,396	260,057	216,410
Loss from operations	(13,730)	(18,247)	(4,462)	(5,457)	(3,686)	(1,703)	(379)	(901)	(41,896)	(6,669)	(7,074)
Other income, net	610	569	463	2,052	583	408	391	410	3,693	1,792	1,107
Loss before provision (benefit) for income taxes	(13,120)	(17,678)	(3,999)	(3,405)	(3,103)	(1,295)	12	(491)	(38,203)	(4,877)	(5,967)
Provision (benefit) for income taxes	142	70,842	(3,453)	(1,236)	(178)	30	(15)	37	66,294	(126)	(847)
Net loss	$ (13,262)	$ (88,520)	$ (546)	$ (2,169)	$ (2,925)	$ (1,325)	$ 27	$ (528)	$ (104,497)	$ (4,751)	$ (5,120)
Net income (loss) per share:
Basic	$ (0.14)	$ (0.96)	$ (0.01)	$ (0.02)	$ (0.03)	$ (0.01)	$ 0.00	$ (0.01)	$ (1.14)	$ (0.05)	$ (0.06)
Diluted	$ (0.14)	$ (0.96)	$ (0.01)	$ (0.02)	$ (0.03)	$ (0.01)	$ 0.00	$ (0.01)	$ (1.14)	$ (0.05)	$ (0.06)
Shares used in per share calculations:
Basic	92,526	92,029	91,689	91,643	91,175	90,774	89,987	89,434	92,017	90,340	88,477
Diluted	92,526	92,029	91,689	91,643	91,175	90,774	93,447	89,434	92,017	90,340	88,477