Cash, Cash Equivalents and Investments (Summary Of Cash, Cash Equivalents And Trading And Available-For-Sale Investments) (Details) - USD ($) $ in Thousands	Feb. 28, 2018	Nov. 30, 2017
Cash, Cash Equivalents and Investments [Line Items]
Amortized Cost Basis	$ 167,778	$ 183,902
Unrealized Gains	0	0
Unrealized Losses	(281)	(293)
Fair Value	167,497	183,609
State and municipal bond obligations [Member]
Cash, Cash Equivalents and Investments [Line Items]
Amortized Cost Basis	35,518	40,458
Unrealized Gains	0	0
Unrealized Losses	(164)	(231)
Fair Value	35,354	40,227
U.S. treasury bonds [Member]
Cash, Cash Equivalents and Investments [Line Items]
Amortized Cost Basis	7,700	3,517
Unrealized Gains	0	0
Unrealized Losses	(38)	(26)
Fair Value	7,662	3,491
Corporate bonds [Member]
Cash, Cash Equivalents and Investments [Line Items]
Amortized Cost Basis	7,449	6,463
Unrealized Gains	0	0
Unrealized Losses	(79)	(36)
Fair Value	7,370	6,427
Cash [Member]
Cash, Cash Equivalents and Investments [Line Items]
Amortized Cost Basis	113,420	130,547
Unrealized Gains	0	0
Unrealized Losses	0	0
Fair Value	113,420	130,547
Money market funds [Member]
Cash, Cash Equivalents and Investments [Line Items]
Amortized Cost Basis	3,691	2,917
Unrealized Gains	0	0
Unrealized Losses	0	0
Fair Value	$ 3,691	$ 2,917