Cash, Cash Equivalents and Investments (Summary Of Cash, Cash Equivalents And Trading And Available-For-Sale Investments) (Details) (USD $) In Thousands, unless otherwise specified	Feb. 28, 2013	Nov. 30, 2012
Cash, Cash Equivalents and Investments [Line Items]
Amortized Cost Basis	$ 351,786	$ 385,640
Unrealized Gains	239	255
Unrealized Losses	(4,208)	(4,357)
Fair Value	347,817	381,538
Cash [Member]
Cash, Cash Equivalents and Investments [Line Items]
Amortized Cost Basis	186,961	176,201
Unrealized Gains	0	0
Unrealized Losses	0	0
Fair Value	186,961	176,201
Money market funds [Member]
Cash, Cash Equivalents and Investments [Line Items]
Amortized Cost Basis	92,256	125,591
Unrealized Gains	0	0
Unrealized Losses	0	0
Fair Value	92,256	125,591
State and municipal bond obligations [Member]
Cash, Cash Equivalents and Investments [Line Items]
Amortized Cost Basis	41,919	50,565
Unrealized Gains	239	255
Unrealized Losses	0	(2)
Fair Value	42,158	50,818
Auction rate securities - municipal bonds [Member]
Cash, Cash Equivalents and Investments [Line Items]
Amortized Cost Basis	27,150	27,175
Unrealized Gains	0	0
Unrealized Losses	(3,635)	(3,755)
Fair Value	23,515	23,420
Auction rate securities - student loans [Member]
Cash, Cash Equivalents and Investments [Line Items]
Amortized Cost Basis	3,500	3,500
Unrealized Gains	0	0
Unrealized Losses	(573)	(599)
Fair Value	2,927	2,901
Corporate bonds [Member]
Cash, Cash Equivalents and Investments [Line Items]
Amortized Cost Basis		2,608
Unrealized Gains		0
Unrealized Losses		(1)
Fair Value		$ 2,607