Restructuring Charges (Narrative) (Details) (USD $)	3 Months Ended			9 Months Ended			12 Months Ended
	Jan. 31, 2014	Jan. 31, 2013	Jan. 31, 2012 site	Jan. 31, 2014	Jan. 31, 2013	Jan. 31, 2014 2012 Restructuring Plan [Member] site	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	$ 48,000	$ 118,000		$ 161,000	$ 979,000	$ 200,000	$ 17,300,000	$ 17,300,000
Recognized recurring operating costs for closed facilities				200,000
Number of manufacturing plants held for sale						2
Net book value of plants recoverable	$ 2,700,000			$ 2,700,000