Selected Quarterly Operating Results (Unaudited) - Summary of Selected Quarterly Operating Results (Details) - USD ($) $ / shares in Units, shares in Thousands, $ 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, 2019	Mar. 31, 2018	Mar. 31, 2017
Revenues:
Total revenues	$ 134,785	$ 130,867	$ 130,321	$ 133,200	$ 135,775	$ 131,715	$ 132,607	$ 130,922	$ 529,173	$ 531,019	$ 509,624
Cost of revenue:
Total cost of revenue	62,057	61,671	61,118	61,851	61,977	61,634	58,755	59,169	246,697	241,535	223,134
Gross profit	72,728	69,196	69,203	71,349	73,798	70,081	73,852	71,753	282,476	289,484	286,490
Operating expenses:
Selling, general and administrative	44,710	41,304	34,229	44,636	65,709	43,563	40,977	42,977	164,879	193,226	163,623
Research and development costs, net	19,813	20,682	18,371	22,128	21,098	20,645	19,527	19,989	80,994	81,259	78,341
Amortization of acquired intangible assets	1,028	1,027	1,121	1,168	1,795	1,956	2,012	2,047	4,344	7,810	10,435
Impairment of assets					3,757					3,757
Restructuring costs	640				481	130			640	611	7,078
Total operating expenses	66,191	63,013	53,721	67,932	92,840	66,294	62,516	65,013	250,857	286,663	259,477
Income from operations	6,537	6,183	15,482	3,417	(19,042)	3,787	11,336	6,740	31,619	2,821	27,013
Interest income	103	44	40	29	19	15	12	9	216	55	14
Interest expense	(595)	(720)	(769)	(730)	(1,073)	(733)	(840)	(677)	(2,814)	(3,323)	(3,156)
Other income (expense), net	(117)	(227)	237	374	85	(41)	15	(22)	267	37	(262)
Income (loss) before provision for (benefit of) income taxes	5,928	5,280	14,990	3,090	(20,011)	3,028	10,523	6,050	29,288	(410)	23,609
Provision for (benefit of) income taxes	2,000	456	1,896	442	(8,964)	1,487	2,493	2,154	4,794	(2,830)	5,368
Net income	$ 3,928	$ 4,824	$ 13,094	$ 2,648	$ (11,047)	$ 1,541	$ 8,030	$ 3,896	$ 24,494	$ 2,420	$ 18,241
Net income (loss) per share:
Basic	$ 0.06	$ 0.07	$ 0.20	$ 0.04	$ (0.17)	$ 0.02	$ 0.13	$ 0.06	$ 0.38	$ 0.04	$ 0.30
Diluted	$ 0.06	$ 0.07	$ 0.20	$ 0.04	$ (0.17)	$ 0.02	$ 0.13	$ 0.06	$ 0.38	$ 0.04	$ 0.29
Weighted-average shares outstanding:
Basic	64,749	64,637	64,265	64,019	63,888	63,706	63,513	62,636	64,417	63,435	61,818
Diluted	64,917	64,776	64,857	64,054	63,888	63,708	63,530	62,643	64,600	63,440	62,010
Recurring
Revenues:
Total revenues	$ 120,151	$ 117,446	$ 116,317	$ 120,007	$ 118,598	$ 118,997	$ 119,441	$ 119,178	$ 473,921	$ 476,214	$ 448,325
Cost of revenue:
Total cost of revenue	48,174	47,997	47,172	48,153	48,856	49,347	47,699	48,458	191,496	194,360	179,245
Software, Hardware, and Other Non-recurring
Revenues:
Total revenues	14,634	13,421	14,004	13,193	17,177	12,718	13,166	11,744	55,252	54,805	61,299
Cost of revenue:
Total cost of revenue	5,959	6,576	7,022	7,154	6,775	6,323	5,947	6,040	26,711	25,085	26,109
Amortization of Capitalized Software Costs and Acquired Intangible Assets
Cost of revenue:
Total cost of revenue	$ 7,924	$ 7,098	$ 6,924	$ 6,544	$ 6,346	$ 5,964	$ 5,109	$ 4,671	$ 28,490	$ 22,090	$ 17,780