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Fair Value Measurements (Details) (Recurring [Member], USD $)
In Thousands, unless otherwise specified
Oct. 31, 2012
Apr. 30, 2012
Assets:    
Cash equivalents $ 61,272 $ 56,698
Total assets 61,272 56,698
Level 1 [Member]
   
Assets:    
Cash equivalents 61,272 56,698
Total assets $ 61,272 $ 56,698