Cash And Investments (Investments With Continuous Unrealized Losses And Their Related Fair Values) (Details) (USD $) In Thousands, unless otherwise specified	Nov. 30, 2011	Nov. 30, 2010
Schedule of Available-for-sale Securities [Line Items]
Fair Value, Less Than 12 Months	$ 24,585	$ 15,903
Less Than 12 Months Unrealized Losses	(16)	(31)
Fair Value, 12 Months or Greater	33,539	39,643
12 Months or Greater Unrealized Losses	(6,361)	(6,557)
Total Fair Value	58,124	55,546
Total Unrealized Losses	(6,377)	(6,588)
State And Municipal Bond Obligations [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair Value, Less Than 12 Months	24,585	6,506
Less Than 12 Months Unrealized Losses	(16)	(10)
Total Fair Value	24,585	6,506
Total Unrealized Losses	(16)	(10)
Auction Rate Securities - Municipal Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair Value, 12 Months or Greater	22,931	23,640
12 Months or Greater Unrealized Losses	(4,269)	(3,560)
Total Fair Value	22,931	23,640
Total Unrealized Losses	(4,269)	(3,560)
Auction Rate Securities - Student Loans [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair Value, 12 Months or Greater	10,608	16,003
12 Months or Greater Unrealized Losses	(2,092)	(2,997)
Total Fair Value	10,608	16,003
Total Unrealized Losses	(2,092)	(2,997)
Corporate Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair Value, Less Than 12 Months		9,397
Less Than 12 Months Unrealized Losses		(21)
Total Fair Value		9,397
Total Unrealized Losses		$ (21)