Supplementary Cash Flow Information (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Apr. 30, 2013	Apr. 30, 2012	Apr. 30, 2011
Supplemental Cash Flow Elements [Abstract]
State and local income tax payments	$ (120)	$ (159)	$ (15)
Federal income tax payments to the Parent	(1,877)	(845)	(348)
Federal income tax refunds			1,598
Interest payments			$ (2)