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Valuation And Qualifying Accounts (Detail) (USD $)
In Thousands, unless otherwise specified
 12 Months Ended
Apr. 30, 2012
Apr. 30, 2011
Apr. 30, 2010
Allowance for Doubtful Accounts [Member]
      
Valuation and Qualifying Accounts Disclosure [Line Items]      
Balance at Beginning of Period $ 9,977 $ 5,983 $ 11,197
Charges to Cost and Expenses 5,732 7,650 3,340
Charges to Other Accounts (220) [1] 413 [1] (50) [1]
Deductions (6,052) [2] (4,069) [2] (8,504) [2]
Balance at End of Period 9,437 9,977 5,983
Deferred Tax Asset Valuation Allowance [Member]
      
Valuation and Qualifying Accounts Disclosure [Line Items]      
Balance at Beginning of Period 26,168 21,037 15,097
Charges to Cost and Expenses 443 15,689 5,940
Charges to Other Accounts    [1]    [1]    [1]
Deductions (1,522) [2] (10,558) [2]    [2]
Balance at End of Period $ 25,089 $ 26,168 $ 21,037
[1] Exchange rate fluctuations.
[2] Allowance for doubtful accounts represents accounts written-off, net of recoveries and deferred tax asset valuation represents release of prior valuation allowances.