Operating Segment and Geographic Information - Additional Information (Detail) $ in Thousands	3 Months Ended								12 Months Ended
	Apr. 30, 2015 USD ($)	Jan. 31, 2015 USD ($)	Oct. 31, 2014 USD ($)	Jul. 31, 2014 USD ($)	Apr. 30, 2014 USD ($)	Jan. 31, 2014 USD ($)	Oct. 31, 2013 USD ($)	Jul. 31, 2013 USD ($)	Apr. 30, 2015 USD ($) Segment	Apr. 30, 2014 USD ($)	Apr. 30, 2013 USD ($)
Segment Reporting Information [Line Items]
Number of operating segment | Segment									1
Number of reportable segment | Segment									1
Revenues from continued operations	$ 48,317	$ 49,562	$ 47,325	$ 45,977	$ 43,078	$ 43,600	$ 41,148	$ 40,319	$ 191,181	$ 168,145	$ 146,812
United States
Segment Reporting Information [Line Items]
Revenues from continued operations									133,700	123,300	105,100
United Kingdom
Segment Reporting Information [Line Items]
Revenues from continued operations									$ 22,900	$ 22,400	$ 18,400