XML 66 R38.htm IDEA: XBRL DOCUMENT v2.4.0.6
Amortized Cost and Fair Values of Marketable Securities Classified as Available-For-Sale Investments (Detail) (USD $)
In Thousands, unless otherwise specified
Oct. 31, 2012
Apr. 30, 2012
Schedule of Available-for-sale Securities [Line Items]    
Amortized Cost $ 44,992 $ 53,497
Gross Unrealized Gains 109 82
Gross Unrealized Losses (19) [1] (21) [1]
Estimated Fair Value 45,082 53,558
Corporate Bonds
   
Schedule of Available-for-sale Securities [Line Items]    
Amortized Cost 40,989 44,498
Gross Unrealized Gains 109 81
Gross Unrealized Losses (19) [1] (16) [1]
Estimated Fair Value 41,079 44,563
Commercial Paper
   
Schedule of Available-for-sale Securities [Line Items]    
Amortized Cost 1,999 5,993
Gross Unrealized Gains   1
Gross Unrealized Losses   (5) [1]
Estimated Fair Value 1,999 5,989
U.S. Treasury And Agency Securities
   
Schedule of Available-for-sale Securities [Line Items]    
Amortized Cost 2,004 3,006
Estimated Fair Value $ 2,004 $ 3,006
[1] There are no marketable securities that have been in a continuous unrealized loss position for 12 months or more.