Quarterly Financial Information (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Apr. 30, 2017	Jan. 31, 2017	Oct. 31, 2016	Jul. 31, 2016	Apr. 30, 2016	Jan. 31, 2016	Oct. 31, 2015	Jul. 31, 2015	Apr. 30, 2017	Apr. 30, 2016	Apr. 30, 2015
Quarterly Financial Information Disclosure [Abstract]
Revenue	$ 50,209	$ 50,525	$ 50,408	$ 50,093	$ 50,709	$ 50,255	$ 49,926	$ 48,876	$ 201,235	$ 199,766	$ 191,181
Cost of revenue	19,596	19,196	18,855	18,756	19,253	18,920	19,146	19,548	76,403	76,867	69,906
Gross profit	30,613	31,329	31,553	31,337	31,456	31,335	30,780	29,328	124,832	122,899	121,275
Sales and marketing	17,803	16,322	15,819	15,304	18,027	16,113	16,502	19,166	65,248	69,808	78,373
Research and development	9,467	9,588	9,959	11,073	10,391	10,199	10,354	10,533	40,087	41,477	37,695
General and administrative	8,343	7,299	8,051	8,259	7,577	6,940	7,643	8,238	31,952	30,398	30,507
Restructuring charges	1,108	0	767	327	1,575	0	0	0	2,202	1,575	0
Sales tax refund	(3,341)	0	0	0	0	0	0	0	(3,341)	0	0
Acquisition-related and other	196	84	120	176	157	332	224	702	576	1,415	4,046
Amortization of acquired intangible assets	309	309	310	309	309	309	310	309	1,237	1,237	1,237
Total operating expenses	33,885	33,602	35,026	35,448	38,036	33,893	35,033	38,948	137,961	145,910	151,858
Operating loss	(3,272)	(2,273)	(3,473)	(4,111)	(6,580)	(2,558)	(4,253)	(9,620)	(13,129)	(23,011)	(30,583)
Total other expense, net	(499)	(332)	(569)	(859)	(384)	(719)	(475)	(712)	(2,259)	(2,290)	(2,527)
Net loss before income taxes	(3,771)	(2,605)	(4,042)	(4,970)	(6,964)	(3,277)	(4,728)	(10,332)	(15,388)	(25,301)	(33,110)
Income tax expense (benefit)	203	123	92	135	165	(163)	124	(88)	553	38	54
Net loss	$ (3,974)	$ (2,728)	$ (4,134)	$ (5,105)	$ (7,129)	$ (3,114)	$ (4,852)	$ (10,244)	$ (15,941)	$ (25,339)	$ (33,164)
Basic and diluted earnings per share	$ (0.05)	$ (0.03)	$ (0.05)	$ (0.06)	$ (0.09)	$ (0.04)	$ (0.06)	$ (0.13)	$ (0.19)	$ (0.31)	$ (0.42)