Restructuring Charges (Narrative) (Details) (USD $)	12 Months Ended			3 Months Ended		12 Months Ended
	Apr. 30, 2014	Apr. 30, 2013	Apr. 30, 2012	Apr. 30, 2009 2009 Restructuring Plan [Member] segment	Jan. 31, 2012 2012 Restructuring Plan [Member] segment	Apr. 30, 2014 2012 Restructuring Plan [Member] segment	Apr. 30, 2014 2012 And 2009 Restructuring Plan [Member]	Apr. 30, 2013 2012 And 2009 Restructuring Plan [Member]	Apr. 30, 2012 2012 And 2009 Restructuring Plan [Member]
Restructuring Cost and Reserve [Line Items]
Plants committed to close				2	2
Pre-tax restructuring charges	$ (234,000)	$ 1,433,000	$ 16,321,000				$ (234,000)	$ 1,400,000	$ 16,300,000
Recognized recurring operating costs for closed facilities						300,000
Number of manufacturing plants held for sale						1
Recognized gain from sale of plant	300,000
Net book value of plants recoverable	$ 1,000,000