Cash, Cash Equivalents and Investments (Investments with Continuous Unrealized Losses and Their Related Fair Values) (Details) (USD $) In Thousands, unless otherwise specified	Aug. 31, 2012	Nov. 30, 2011
Schedule of Available-for-sale Securities [Line Items]
Fair Value, Less Than 12 Months	$ 13,598	$ 24,585
Unrealized Losses, Less Than 12 Months	(5)	(16)
Fair Value, 12 Months or Greater	31,285	33,539
Unrealized Losses, 12 Months or Greater	(5,690)	(6,361)
Total, Fair Value	44,883	58,124
Total, Unrealized Losses	(5,695)	(6,377)
State And Municipal Bond Obligations [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair Value, Less Than 12 Months	10,980	24,585
Unrealized Losses, Less Than 12 Months	(4)	(16)
Total, Fair Value	10,980	24,585
Total, Unrealized Losses	(4)	(16)
Auction Rate Securities - Municipal Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair Value, 12 Months or Greater	23,354	22,931
Unrealized Losses, 12 Months or Greater	(3,821)	(4,269)
Total, Fair Value	23,354	22,931
Total, Unrealized Losses	(3,821)	(4,269)
Auction Rate Securities - Student Loans [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair Value, 12 Months or Greater	7,931	10,608
Unrealized Losses, 12 Months or Greater	(1,869)	(2,092)
Total, Fair Value	7,931	10,608
Total, Unrealized Losses	(1,869)	(2,092)
Corporate Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair Value, Less Than 12 Months	2,618
Unrealized Losses, Less Than 12 Months	(1)
Total, Fair Value	2,618
Total, Unrealized Losses	$ (1)