Cash, Cash Equivalents and Investments (Summary Of Cash, Cash Equivalents And Trading And Available-For-Sale Investments) (Details) - USD ($) $ in Thousands	Aug. 31, 2016	Nov. 30, 2015
Cash, Cash Equivalents and Investments [Line Items]
Amortized Cost Basis	$ 232,638	$ 241,276
Unrealized Gains	50	30
Unrealized Losses	(4)	(27)
Fair Value	232,684	241,279
State and municipal bond obligations [Member]
Cash, Cash Equivalents and Investments [Line Items]
Amortized Cost Basis	34,489	20,387
Unrealized Gains	43	30
Unrealized Losses		0
Fair Value	34,532	20,417
U.S. treasury bonds [Member]
Cash, Cash Equivalents and Investments [Line Items]
Amortized Cost Basis	6,534	3,109
Unrealized Gains	0	0
Unrealized Losses		(15)
Fair Value	6,534	3,094
U.S. government agency bonds [Member]
Cash, Cash Equivalents and Investments [Line Items]
Amortized Cost Basis	525	1,645
Unrealized Gains	1	0
Unrealized Losses	(4)	(4)
Fair Value	522	1,641
Corporate bonds [Member]
Cash, Cash Equivalents and Investments [Line Items]
Amortized Cost Basis	3,006	3,756
Unrealized Gains	6	0
Unrealized Losses		(8)
Fair Value	3,012	3,748
Cash [Member]
Cash, Cash Equivalents and Investments [Line Items]
Amortized Cost Basis	179,548	186,241
Unrealized Gains	0	0
Unrealized Losses		0
Fair Value	179,548	186,241
Money market funds [Member]
Cash, Cash Equivalents and Investments [Line Items]
Amortized Cost Basis	8,536	26,138
Unrealized Gains	0	0
Unrealized Losses		0
Fair Value	$ 8,536	$ 26,138