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           Other Comprehensive (Loss)/Income 
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        3 Months Ended | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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           Aug. 31, 2012 
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| Other Comprehensive (Loss)/Income [Abstract] | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Other Comprehensive (Loss)/Income | 
   
    Note G: Other Comprehensive (Loss)/Income Other comprehensive (loss)/income results from items deferred on the Consolidated Balance Sheets in stockholders’ equity. The change in unrealized gains and losses, net of applicable taxes, related to available-for-sale securities is the primary component reported in accumulated other comprehensive income in the Consolidated Balance Sheets. Other comprehensive (loss)/income, is as follows: 
 
 As of August 31, 2012, accumulated other comprehensive income was $37.3 million, which was net of taxes of $21.5 million. As of May 31, 2012, accumulated other comprehensive income was $37.7 million, which was net of taxes of $21.8 million. Accumulated other comprehensive income is comprised of unrealized gains/losses, net of tax.  | 
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