Restructuring Charges (Narrative) (Details) $ in Thousands	3 Months Ended		12 Months Ended
	Apr. 30, 2014 USD ($)	Jan. 31, 2012 plant	Apr. 30, 2016 USD ($)	Apr. 30, 2015 USD ($)	Apr. 30, 2014 USD ($)
Restructuring Cost and Reserve [Line Items]
Pre-tax restructuring charges			$ 0	$ (240)	$ (234)
Recognized gain from sale of plant	$ 300		300
2012 Restructuring Plan [Member]
Restructuring Cost and Reserve [Line Items]
Plants committed to close | plant		2
2012 And 2009 Restructuring Plan [Member]
Restructuring Cost and Reserve [Line Items]
Pre-tax restructuring charges			$ (200)	$ (200)