Quarterly Operating Results (Detail) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended								12 Months Ended
	Apr. 30, 2013	Jan. 31, 2013	Oct. 31, 2012	Jul. 31, 2012	Apr. 30, 2012	Jan. 31, 2012	Oct. 31, 2011	Jul. 31, 2011	Apr. 30, 2013		Apr. 30, 2012		Apr. 30, 2011
Quarterly Financial Information [Line Items]
Revenue	$ 43,330	$ 42,678	$ 38,626	$ 35,662	$ 31,431	$ 27,602	$ 25,015	$ 22,088	$ 160,296		$ 106,136		$ 64,482
Cost of revenue	14,158	14,217	14,099	12,633	10,325	9,514	8,805	7,797	55,107	[1]	36,441	[1]	25,615	[1]
Gross profit	29,172	28,461	24,527	23,029	21,106	18,088	16,210	14,291	105,189		69,695		38,867
Operating expenses:
Sales and marketing	23,003	20,710	17,850	15,322	14,257	12,152	12,125	11,192	76,885	[1]	49,726	[1]	34,568	[1]
Research and development	8,690	8,914	7,948	7,494	6,811	6,059	4,576	3,343	33,046	[1]	20,789	[1]	10,847	[1]
General and administrative	10,744	8,783	7,484	16,196	6,047	5,934	4,815	5,099	43,207	[1]	21,895	[1]	13,156	[1]
Acquisition-related and other	7,441	2,021	1,366	1,384					12,212
Amortization of acquired intangible assets	1,381	1,165	898	480					3,924
Total operating expenses	51,259	41,593	35,546	40,876	27,115	24,145	21,516	19,634	169,274		92,410		58,571
Operating loss	(22,087)	(13,132)	(11,019)	(17,847)	(6,009)	(6,057)	(5,306)	(5,343)	(64,085)		(22,715)		(19,704)
Total other income (expense), net	(473)	12	51	(404)	(15)	(337)	(367)	(84)	(814)		(803)		208
Net loss before income taxes	(22,560)	(13,120)	(10,968)	(18,251)	(6,024)	(6,394)	(5,673)	(5,427)	(64,899)		(23,518)		(19,496)
Income tax expense (benefit)	584	(2,293)	274	288	343	181	178	109	(1,147)		811		561
Net loss	$ (23,144)	$ (10,827)	$ (11,242)	$ (18,539)	$ (6,367)	$ (6,575)	$ (5,851)	$ (5,536)	$ (63,752)		$ (24,329)		$ (20,057)
Basic and diluted net loss per share (applicable to common stockholders)	$ (0.32)	$ (0.15)	$ (0.16)	$ (0.30)	$ (0.13)	$ (0.34)	$ (0.30)	$ (0.29)	$ (0.92)		$ (0.92)		$ (1.13)

[1] Includes stock-based expense as follows: Cost of revenue $ 1,704 $ 1,220 $ 978 Sales and marketing 4,250 1,869 1,122 Research and development 3,126 1,326 731 General and administrative 13,373 3,295 1,850