Cash, Cash Equivalents and Investments (Fair Value of Debt Securities by Contractual Maturity) (Details) (USD $) In Thousands, unless otherwise specified					12 Months Ended
	Nov. 30, 2012		Nov. 30, 2011		Nov. 30, 2012 Maximum [Member]	Nov. 30, 2012 Minimum [Member]
Cash, Cash Equivalents and Investments [Line Items]
Due in one year or less	$ 55,001	[1]	$ 104,620	[1]
Due after one year	24,745		31,225
Total	$ 79,746		$ 135,845
Remaining contractual maturities of investments (in years)					30 years	11 years

[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 11 to 30 years.