Debt (Narrative) (Details) (USD $)	3 Months Ended		12 Months Ended				12 Months Ended			12 Months Ended		12 Months Ended
	May 31, 2011	Feb. 28, 2011	Aug. 31, 2012	Aug. 31, 2011	Aug. 31, 2010	Aug. 31, 2012 Co-Issuers And Guarantor [Member]	Aug. 31, 2012 2011 Fixed Rate Notes [Member]	Aug. 31, 2011 2011 Fixed Rate Notes [Member]	May 20, 2011 2011 Fixed Rate Notes [Member]	Aug. 31, 2012 2011 Variable Rate Notes [Member]	May 20, 2011 2011 Variable Rate Notes [Member]	Aug. 31, 2012 2011 Variable Funding [Member]	Aug. 31, 2011 2011 Variable Funding [Member]	Aug. 31, 2012 2011 Notes [Member]	Aug. 31, 2011 2011 Notes [Member]	Aug. 31, 2012 2011 Variable Funding Notes [Member]	Feb. 28, 2011 2006 Variable Funding Notes [Member]	Aug. 31, 2012 Interest Rate Upward Adjustment Due To Nonpayment [Member]
Debt Instrument [Line Items]
Future maturities of long-term debt, 2013			$ 15,200,000
Future maturities of long-term debt, 2014			15,300,000
Future maturities of long-term debt, 2015			15,000,000
Future maturities of long-term debt, 2016			15,000,000
Future maturities of long-term debt, 2017			15,000,000
Debt instrument, face amount									500,000,000		100,000,000
Debt issuance date														May 20, 2011
Senior secured notes interest rate, percentage							5.40%											5.00%
Debt instrument, maturity year							May 21, 2018							May 20, 2041		May 20, 2016
Long term debt fixed rate notes including accrued interest carrying value			482,000,000	497,000,000			482,000,000	497,000,000
Weighted-average interest cost, percentage							5.90%	5.90%
Expected life of debt instrument							7 years			5 years
Interest rate percentage												3.75%
Annual commitment fee payable, percentage												0.50%
Additional borrowed amount													35,000,000
Proceeds from issuance of debt				535,000,000											535,000,000
Payment of loan costs															16,400,000
Restricted cash			18,100,000			18,100,000
Total assets held by indirect subsidiaries			680,760,000	679,742,000		356,600,000
Early extinguishment of debt, gain/loss	(28,200,000)	5,200,000		(23,035,000)	(314,000)
Prepayment premium and write off of unamortized deferred loan fees	25,300,000
Repurchased of notes																	$ 62,500,000