Restructuring Charges (Narrative) (Details) (USD $)	3 Months Ended				12 Months Ended
	Jul. 31, 2014	Jul. 31, 2013	Jan. 31, 2012 manufacturing_plant	Jul. 31, 2014 2012 Restructuring Plan [Member] manufacturing_plant	Apr. 30, 2014 2012 Restructuring Plan [Member]	Apr. 30, 2013 2012 Restructuring Plan [Member]	Apr. 30, 2012 2012 Restructuring Plan [Member]
Restructuring Cost and Reserve [Line Items]
Plants committed to close			2
Pre-tax restructuring charges	$ 3,000	$ 82,000		$ 3,000	$ 17,100,000	$ 17,100,000	$ 17,100,000
Recognized recurring operating costs for closed facilities	28,000
Number of manufacturing plants held for sale				1
Net book value of plants recoverable	$ 1,000,000