Term Loan and Line of Credit (Narrative) (Details) - Credit Agreement [Member] - USD ($)	3 Months Ended		9 Months Ended
	Aug. 31, 2016	Aug. 31, 2015	Aug. 31, 2016	Aug. 31, 2015	Dec. 02, 2014
Line of Credit Facility [Line Items]
Term loan					$ 150,000,000
Unsecured credit facility					150,000,000
Additional borrowing capacity available					75,000,000
Fair value of term loan	$ 136,900,000		$ 136,900,000
Due in next 12 months	13,100,000		13,100,000
Principal payments for years one and two	1,900,000		1,900,000
Principal payments for years three and four	3,800,000		3,800,000
Principal payments for years five and thereafter	5,600,000		$ 5,600,000
Interest rate during period (as a percent)			2.25%
Debt issuance cost	1,800,000		$ 1,800,000
Amortization of debt issuance costs	100,000	$ 100,000	300,000	$ 300,000
Letter of credit [Member]
Line of Credit Facility [Line Items]
Unsecured credit facility					25,000,000.0
Line of credit facility outstanding amount	500,000		500,000
Revolving line of credit [Member]
Line of Credit Facility [Line Items]
Line of credit facility outstanding amount	$ 0		$ 0
Swing line loans [Member]
Line of Credit Facility [Line Items]
Unsecured credit facility					$ 25,000,000.0