Stockholders' Equity - Additional Information (Detail) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended		6 Months Ended		3 Months Ended		6 Months Ended		3 Months Ended		6 Months Ended				3 Months Ended		6 Months Ended
	Oct. 31, 2014	Oct. 31, 2013	Oct. 31, 2014	Oct. 31, 2013	Oct. 31, 2014 Stock Options [Member]	Oct. 31, 2013 Stock Options [Member]	Oct. 31, 2014 Stock Options [Member]	Oct. 31, 2013 Stock Options [Member]	Oct. 31, 2014 Restricted Stock, Restricted Stock Units and Performance Stock Units [Member]	Oct. 31, 2013 Restricted Stock, Restricted Stock Units and Performance Stock Units [Member]	Oct. 31, 2014 Restricted Stock, Restricted Stock Units and Performance Stock Units [Member]	Oct. 31, 2013 Restricted Stock, Restricted Stock Units and Performance Stock Units [Member]	Oct. 31, 2014 Restricted Stock and Restricted Stock Unit [Member]	Oct. 31, 2014 Performance Stock Units [Member]	Oct. 31, 2014 Employee Stock Purchase Plan [Member]	Oct. 31, 2013 Employee Stock Purchase Plan [Member]	Oct. 31, 2014 Employee Stock Purchase Plan [Member]	Oct. 31, 2013 Employee Stock Purchase Plan [Member]	Oct. 31, 2014 Non-Employee Director [Member] Restricted Stock Awards [Member]	Oct. 31, 2014 Employee [Member] Restricted Stock Awards [Member]	Oct. 31, 2014 2006 Stock Incentive Plan [Member] Minimum [Member]	Oct. 31, 2014 2006 Stock Incentive Plan [Member] Maximum [Member]	Oct. 31, 2014 Class A Common Stock [Member] 2006 Stock Incentive Plan [Member]	Apr. 30, 2007 Class A Common Stock [Member] 2006 Stock Incentive Plan [Member]
Limited Partners' Capital Account [Line Items]
Common stock, issued shares																								2,475,000
Number of shares available for future grant																							994,000
Options vesting period																			3 years	3 years	1 year	4 years
Options granted period																						10 years
Stock-based compensation expense					$ 165	$ 88	$ 275	$ 203	$ 465	$ 475	$ 897	$ 966			$ 16	$ 15	$ 37	$ 39
Unrecognized stock-based compensation expense					$ 1,200		$ 1,200						$ 2,685	$ 2,479
Unrecognized stock-based compensation expense, weighted average period							1 year 9 months 18 days						1 year 10 months 24 days	6 months
Expected dividend yield	0.00%		0.00%
Stock Options, Granted		0	200,000	0