Operating Segment and Geographic Information - Additional Information (Details) $ in Thousands	3 Months Ended									12 Months Ended
	Apr. 30, 2016 USD ($)	[1]	Jan. 31, 2016 USD ($)	Oct. 31, 2015 USD ($)	Jul. 31, 2015 USD ($)	Apr. 30, 2015 USD ($)	Jan. 31, 2015 USD ($)	Oct. 31, 2014 USD ($)	Jul. 31, 2014 USD ($)	Apr. 30, 2016 USD ($)	Apr. 30, 2015 USD ($)	Apr. 30, 2014 USD ($)
Revenues from External Customers and Long-Lived Assets [Line Items]
Number of Operating Segments										1
Number of Reportable Segments										1
Revenue	$ 50,709		$ 50,255	$ 49,926	$ 48,876	$ 48,317	$ 49,562	$ 47,325	$ 45,977	$ 199,766	$ 191,181	$ 168,145
UNITED KINGDOM
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue										26,000	22,900	22,400
UNITED STATES
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue										$ 140,800	$ 133,700	$ 123,300

[1] During the fourth quarter of fiscal 2016, the Company recorded out of period adjustments related to errors in the timing of recognition of revenue, for which all required criteria had been satisfied in prior periods. The cumulative effect of out of period adjustments for the fourth quarter of fiscal 2016 was a $0.9 million increase in revenue. The Company has determined that these adjustments were not material to any prior annual or interim periods, and the resulting correction is not material to its annual results for fiscal 2016 or to the trend in earnings.