Cash, Cash Equivalents and Investments (Summary Of Cash, Cash Equivalents And Trading And Available-For-Sale Investments) (Details) - USD ($) $ in Thousands	Aug. 31, 2018	Nov. 30, 2017
Cash, Cash Equivalents and Investments [Line Items]
Amortized Cost Basis	$ 138,093	$ 183,902
Unrealized Gains	0	0
Unrealized Losses	(212)	(293)
Fair Value	137,881	183,609
State and municipal bond obligations
Cash, Cash Equivalents and Investments [Line Items]
Amortized Cost Basis	24,349	40,458
Unrealized Gains	0	0
Unrealized Losses	(125)	(231)
Fair value of financial assets	24,224	40,227
U.S. treasury bonds
Cash, Cash Equivalents and Investments [Line Items]
Amortized Cost Basis	6,715	3,517
Unrealized Gains	0	0
Unrealized Losses	(25)	(26)
Fair value of financial assets	6,690	3,491
Corporate bonds
Cash, Cash Equivalents and Investments [Line Items]
Amortized Cost Basis	8,332	6,463
Unrealized Gains	0	0
Unrealized Losses	(62)	(36)
Fair value of financial assets	8,270	6,427
Cash
Cash, Cash Equivalents and Investments [Line Items]
Amortized Cost Basis	92,827	130,547
Unrealized Gains	0	0
Unrealized Losses	0	0
Fair Value	92,827	130,547
Money market funds
Cash, Cash Equivalents and Investments [Line Items]
Amortized Cost Basis	5,870	2,917
Unrealized Gains	0	0
Unrealized Losses	0	0
Fair value of financial assets	$ 5,870	$ 2,917