Term Loan and Line of Credit (Narrative) (Details) - USD ($)	3 Months Ended		9 Months Ended
	Aug. 31, 2017	Aug. 31, 2016	Aug. 31, 2017	Aug. 31, 2016	Dec. 02, 2014
Line of Credit Facility [Line Items]
Unamortized debt issuance costs	$ 800,000		$ 800,000
Unamortized debt issuance costs deducted from current portion of long-term debt	400,000		400,000
Unamortized debt issuance costs deducted from long-term debt	400,000		400,000
Credit Agreement [Member]
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	123,800,000		123,800,000
Due in next 12 months	15,000,000		15,000,000
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)			3.00%
Debt issuance cost	1,800,000		$ 1,800,000
Amortization of debt issuance costs	100,000	$ 100,000	300,000	$ 300,000
Credit Agreement [Member] | Swing line loans [Member]
Line of Credit Facility [Line Items]
Unsecured credit facility					25,000,000.0
Credit Agreement [Member] | Letter of credit [Member]
Line of Credit Facility [Line Items]
Unsecured credit facility					$ 25,000,000.0
Line of credit facility outstanding amount	1,400,000		1,400,000
Credit Agreement [Member] | Revolving line of credit [Member]
Line of Credit Facility [Line Items]
Line of credit facility outstanding amount	$ 0		$ 0