Employee Retirement Plan (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Apr. 30, 2014	Apr. 30, 2013	Apr. 30, 2012
Defined Contribution Plan Disclosure [Line Items]
Defined contribution cost recognized	$ 0.3	$ 0.3	$ 0.4
Maximum [Member]
Defined Contribution Plan Disclosure [Line Items]
Employee contribution, percentage of compensation	100.00%
Employer contribution, matching percentage	6.00%