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Cash, Cash Equivalents And Investments (Fair Value Of Debt Securities By Contractual Maturity) (Details) (USD $)
In Thousands, unless otherwise specified
 3 Months Ended
Feb. 29, 2012
Nov. 30, 2011
Cash, Cash Equivalents And Investments [Abstract]    
Due in one year or less $ 83,475 [1] $ 104,620 [1]
Due after one year 33,337 31,225
Total $ 116,812 $ 135,845
Remaining contractual maturities of investments, minimum period (in years) 12  
Remaining contractual maturities of investments, maximum period, years (in years) 31  
[1] Includes ARS which are tendered for interest-rate setting purposes periodically throughout the year. Beginning in February 2008, auctions for these securities began to fail, and therefore these investments currently lack short-term liquidity. The remaining contractual maturities of these securities range from 12 to 31 years.