Subsequent Event (Details) (USD $)	0 Months Ended	12 Months Ended			0 Months Ended	1 Months Ended		0 Months Ended
	Dec. 19, 2011 months years	Nov. 30, 2011 months	Nov. 30, 2009	Nov. 30, 2009 Unsecured Debt [Member]	Dec. 19, 2011 Cash Borrowings [Member]	Dec. 31, 2011 Cash Borrowings [Member]	Nov. 30, 2011 Cash Borrowings [Member]	Dec. 19, 2011 Credit Agreement [Member]	Nov. 30, 2011 Credit Agreement [Member]	Dec. 19, 2011 Letters Of Credit [Member]	Nov. 30, 2011 Letters Of Credit [Member]	Dec. 19, 2011 Swing Line Loans [Member]	Nov. 30, 2011 Swing Line Loans [Member]	Dec. 31, 2011 Revolving Line Of Credit [Member]	Nov. 30, 2011 Revolving Line Of Credit [Member]	Dec. 19, 2011 Maximum [Member]	Nov. 30, 2011 Maximum [Member]	Nov. 30, 2011 Maximum [Member] Swing Line Loans [Member]	Dec. 19, 2011 Minimum [Member]	Nov. 30, 2011 Minimum [Member]	Nov. 30, 2011 Minimum [Member] Swing Line Loans [Member]
Subsequent Event [Line Items]
Revolving credit facility, maturity date								December 19, 2016
Revolving credit facility, maximum capacity				$ 150,000,000		$ 250,000,000	$ 150,000,000			$ 50,000,000	$ 25,000,000	$ 10,000,000	$ 10,000,000	$ 250,000,000	$ 20,000,000
Revolving credit facility, increase in cash borrowings					100,000,000	100,000,000
Margin on base rates																1.00%		3.00%	0.25%		2.25%
Line Of Credit Spread Over Base Rate																1.00%		3.00%	0.25%		2.25%
Spread over LIBOR	1.00%															2.00%	4.00%		1.25%	3.25%
LIBOR interest period (in months)	1	1
Margin on federal fund	0.50%
Loan origination fees and issuance costs	2,000,000		2,317,000
Amortization of interest expense (in years)	5
Interest coverage ratio																			3.5	3.5
Leverage ratio																2.5	2.5
Revolving credit facility amount outstanding						$ 100,000,000			$ 30,000,000