Provision for Income Taxes - Narrative (Details) - USD ($) $ in Thousands	12 Months Ended
	Apr. 30, 2016	Apr. 30, 2015
Tax Credit Carryforward [Line Items]
Deferred tax assets, valuation allowance	$ 19,071	$ 15,212
Liabilities, other than long-term debt, noncurrent	165
Domestic Tax Authority [Member]
Tax Credit Carryforward [Line Items]
Operating loss carryforwards	$ 36,000	26,000
Operating loss carryforwards, expiration year	2022
Foreign Tax Authority [Member]
Tax Credit Carryforward [Line Items]
Operating loss carryforwards	$ 900	$ 1,000