Cash And Investments (Fair Value Of Debt Securities By Contractual Maturity) (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Nov. 30, 2011 years		Nov. 30, 2010
Cash And Investments [Abstract]
Due in one year or less	$ 104,620	[1]	$ 70,285	[1]
Due after one year	31,225		14,621
Total	$ 135,845		$ 84,906
Remaining contractual maturities of investments, minimum period (in years)	12
Remaining contractual maturities of investments, maximum period (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 final maturities of these securities range from 12 to 31 years.