Supplementary Cash Flow Information (Details) - USD ($) $ in Thousands	12 Months Ended
	Apr. 30, 2015	Apr. 30, 2014	Apr. 30, 2013
Supplemental Cash Flow Elements [Abstract]
State and local income tax payments	$ 238	$ 114	$ 120
Federal income tax payments to the Parent	$ 3,366	$ 2,254	$ 1,877