Line of Credit (Details) (USD $)	9 Months Ended
	Aug. 31, 2012
Line of Credit Facility [Line Items]
Unsecured credit facility	$ 150,000,000
Additional borrowing capacity	75,000,000
Line of credit facility outstanding amount	0
Letters of credit outstanding amount	200,000
Standby letters of credit [Member]
Line of Credit Facility [Line Items]
Additional borrowing capacity	25,000,000
Swing line loans [Member]
Line of Credit Facility [Line Items]
Additional borrowing capacity	$ 20,000,000