Cash, Cash Equivalents and Investments (Fair Value of Debt Securities by Contractual Maturity) (Details) (USD $) In Thousands, unless otherwise specified	9 Months Ended
	Aug. 31, 2012		Nov. 30, 2011
Investments and Cash [Abstract]
Due in one year or less	$ 60,959	[1]	$ 104,620	[1]
Due after one year	28,135		31,225
Total	$ 89,094		$ 135,845
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 contractual maturities of these securities range from 12 to 31 years.