Quarterly report pursuant to Section 13 or 15(d)

Restructuring Liability (Schedule Of Changes In Restructuring Liability) (Details)

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Restructuring Liability (Schedule Of Changes In Restructuring Liability) (Details) (USD $)
 3 Months Ended 9 Months Ended
Jan. 31, 2012
Jan. 31, 2012
Jan. 31, 2011
Apr. 30, 2011
Restructuring Cost and Reserve [Line Items]        
Liability, Beginning period $ 3,076,000 $ 4,921,000    
Restructuring (reductions) charges, net 929,000 929,000 2,130,000  
Reductions for cash payments (639,000) (2,346,000)    
Exchange rate fluctuations (105,000) (243,000)    
Liability, Ending period 3,261,000 3,261,000    
Restructuring liability included in other long-term liabilities 1,500,000 1,500,000   2,100,000
Long-term restructuring liability, payment term seven years seven years    
Severance [Member]
        
Restructuring Cost and Reserve [Line Items]        
Liability, Beginning period 639,000 978,000    
Restructuring (reductions) charges, net (324,000) (324,000)    
Reductions for cash payments (196,000) (527,000)    
Exchange rate fluctuations (24,000) (32,000)    
Liability, Ending period 95,000 95,000    
Facilities [Member]
        
Restructuring Cost and Reserve [Line Items]        
Liability, Beginning period 2,437,000 3,943,000    
Restructuring (reductions) charges, net 1,253,000 1,253,000    
Reductions for cash payments (443,000) (1,819,000)    
Exchange rate fluctuations (81,000) (211,000)    
Liability, Ending period $ 3,166,000 $ 3,166,000