Cash, Cash Equivalents and Investments (Summary Of Cash, Cash Equivalents And Trading And Available-For-Sale Investments) (Details) - USD ($) $ in Thousands	May 31, 2017	Nov. 30, 2016
Cash, Cash Equivalents and Investments [Line Items]
Amortized Cost Basis	$ 245,099	$ 249,894
Unrealized Gains	11	0
Unrealized Losses	(28)	(140)
Fair Value	245,082	249,754
State and municipal bond obligations [Member]
Cash, Cash Equivalents and Investments [Line Items]
Amortized Cost Basis	37,195	32,831
Unrealized Gains	11	0
Unrealized Losses	0	(107)
Fair value of financial assets	37,206
Fair Value		32,724
U.S. treasury bonds [Member]
Cash, Cash Equivalents and Investments [Line Items]
Amortized Cost Basis	5,680	6,542
Unrealized Gains	0	0
Unrealized Losses	(28)	(29)
Fair value of financial assets	5,652
Fair Value		6,513
Corporate bonds [Member]
Cash, Cash Equivalents and Investments [Line Items]
Amortized Cost Basis	4,338	3,485
Unrealized Gains	0	0
Unrealized Losses	0	(4)
Fair value of financial assets	4,338
Fair Value		3,481
Cash [Member]
Cash, Cash Equivalents and Investments [Line Items]
Amortized Cost Basis	191,940	196,863
Unrealized Gains	0	0
Unrealized Losses	0	0
Fair Value	191,940	196,863
Money market funds [Member]
Cash, Cash Equivalents and Investments [Line Items]
Amortized Cost Basis	5,946	10,173
Unrealized Gains	0	0
Unrealized Losses	0	0
Fair value of financial assets	$ 5,946
Fair Value		$ 10,173