Stockholders' Equity - Accumulated Other Comprehensive Income (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Jul. 31, 2014	Jul. 31, 2013
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	$ 39
Other comprehensive income (loss), net of tax	12	(125)
Ending balance	51
Marketable Securities [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	39
Other comprehensive income, net of tax before reclassifications	12
Amounts reclassified from accumulated other comprehensive income
Other comprehensive income (loss), net of tax	12
Ending balance	$ 51