Long-Term Debt And Line Of Credit (Details) (USD $)	9 Months Ended
	Aug. 31, 2011	Feb. 28, 2011	Nov. 30, 2010	Aug. 31, 2010	Nov. 30, 2009	Jun. 30, 2003
Mortgage note payable	$ 38,700,000		$ 40,400,000			$ 54,000,000
Mortgage note payable amortization period (years)	20
Mortgage note payable fixed interest rate	5.50%
Debt principal	38,687,000
Minimum cash reserve for acquiring another company	272,215,000		243,989,000	288,831,000	292,529,000
Revolving credit facility outstanding	0	0
Unsecured revolving credit facility maturity date	Nov. 01, 2012
Spread over LIBOR	1.00%
Margin on federal fund	0.50%
Loan origination fee and issuance costs	2,300,000
Default applicable interest rate on all obligations	2.00%
Unrestricted cash and cash equivalents to be reserved for credit agreement reacquire	120,000,000
Additional letter of credit	5,400,000
Bank guarantees	13,000,000
Restricted cash	15,600,000		10,500,000
Maximum [Member]
Margin on base rates	3.00%
Spread over LIBOR	4.00%
Line of credit facility, commitment fee percentage	0.75%
Interest coverage ratio	1.0
Leverage ratio	1.0
Maximum [Member] | Swing Line Loans [Member]
Margin on base rates	3.00%
Minimum [Member]
Minimum cash reserve for acquiring another company	50,000,000
Margin on base rates	2.25%
Spread over LIBOR	3.25%
Line of credit facility, commitment fee percentage	0.50%
Interest coverage ratio	3.5
Leverage ratio	2.5
Minimum [Member] | Swing Line Loans [Member]
Margin on base rates	2.25%
Mortgage Note [Member]
Debt principal	34,400,000
Unsecured Debt [Member]
Revolving credit facility maximum capacity					150,000,000
Cash Borrowing [Member]
Revolving credit facility maximum capacity	150,000,000
Letter Of Credit [Member]
Revolving credit facility maximum capacity	25,000,000
Swing Line Loans [Member]
Revolving credit facility maximum capacity	10,000,000
Revolving Line Of Credit [Member]
Revolving credit facility maximum capacity	20,000,000
Revolving credit facility outstanding	0	0
Line of credit maturity date	November 2012
Letter Of Credit One [Member]
Revolving credit facility outstanding	13,000,000
Letter Of Credit Two [Member]
Revolving credit facility outstanding	1,100,000
Letter Of Credit Three [Member]
Revolving credit facility outstanding	500,000
Guarantee Credit Line [Member]
Revolving credit facility maximum capacity	14,400,000
Financial Institution [Member]
Unrestricted cash and cash equivalents to be reserved for credit agreement reacquire	80,000,000
Cash Borrowing And Letter Of Credit [Member]
Revolving credit facility maximum capacity	$ 20,000,000