Commitments and Contingencies (Details) (USD $)	12 Months Ended
	Apr. 30, 2013	Apr. 30, 2012	Apr. 30, 2011
Future minimum lease payments under noncancelable operating leases
2014	$ 4,324,000
2015	2,952,000
2016	1,919,000
2017	856,000
2018	137,000
Total	10,188,000
Rental expense under operating leases	$ 4,349,000	$ 3,995,000	$ 3,812,000