Provision for Income Taxes - Narrative (Details) - USD ($) $ in Thousands	12 Months Ended
	Apr. 30, 2018	Apr. 30, 2017
Tax Credit Carryforward [Line Items]
One-time reduction of deferred tax assets	$ 7,600
Deferred tax assets, valuation allowance	14,409	$ 21,779
Liabilities, other than long-term debt, noncurrent	151
Domestic Tax Authority
Tax Credit Carryforward [Line Items]
Operating loss carryforwards	$ 41,000	$ 41,000
Operating loss carryforwards, expiration year	2025
Foreign Tax Authority
Tax Credit Carryforward [Line Items]
Operating loss carryforwards	$ 890