Consolidated Valuation Accounts (Detail) (Allowance for Doubtful Accounts, USD $) In Thousands, unless otherwise specified	12 Months Ended
	Apr. 30, 2014		Apr. 30, 2013		Apr. 30, 2012
Allowance for Doubtful Accounts
Valuation and Qualifying Accounts Disclosure [Line Items]
Balance at beginning of year	$ 337		$ 171		$ 243
Amounts charged to expense	(56)		216		238
Other Additions	86	[1]	0	[1]	0	[1]
Deductions	145	[2]	50	[2]	310	[2]
Balance at end of year	$ 222		$ 337		$ 171

[1] Recovery of previously written-off amounts.

[2] Write-off of uncollectible accounts.