Debt (Narrative) (Details) (USD $)	3 Months Ended				12 Months Ended				12 Months Ended	3 Months Ended		12 Months Ended			12 Months Ended			12 Months Ended
	Aug. 31, 2013	Feb. 28, 2013	May 31, 2011	Feb. 28, 2011	Aug. 31, 2013	Aug. 31, 2011	Aug. 31, 2012	Aug. 31, 2013 Co-Issuers And Guarantor [Member]	Aug. 31, 2013 2013 Fixed Rate Notes [Member]	Aug. 31, 2013 2011 Fixed Rate Notes [Member]	Feb. 28, 2013 2011 Fixed Rate Notes [Member]	Aug. 31, 2013 2011 Fixed Rate Notes [Member]	Aug. 31, 2012 2011 Fixed Rate Notes [Member]	May 20, 2011 2011 Fixed Rate Notes [Member]	Aug. 31, 2013 2011 Variable Rate Notes [Member]	May 31, 2013 2011 Variable Rate Notes [Member]	May 20, 2011 2011 Variable Rate Notes [Member]	Aug. 31, 2013 2011 Notes [Member]	Aug. 31, 2011 2011 Notes [Member]	Aug. 31, 2013 2011 Notes and 2013 Fixed Rate Notes [Member]	Feb. 28, 2011 2006 Variable Funding Notes [Member]	Aug. 31, 2013 Interest Rate Upward Adjustment Due To Nonpayment [Member]
Debt Instrument [Line Items]
Future maturities of long-term debt, 2014	$ 10,000,000				$ 10,000,000
Future maturities of long-term debt, 2015	9,800,000				9,800,000
Future maturities of long-term debt, 2016	9,800,000				9,800,000
Future maturities of long-term debt, 2017	9,800,000				9,800,000
Future maturities of long-term debt, 2018	253,000,000				253,000,000
Debt instrument, face amount									155,000,000					500,000,000			100,000,000
Debt issuance date																		May 20, 2011
Debt prepayment										155,000,000	20,000,000
Senior secured notes interest rate, percentage									3.75%	5.40%		5.40%										5.00%
Debt instrument, maturity year												May 21, 2018			May 21, 2018					May 20, 2041
Long term debt fixed rate notes including accrued interest carrying value	447,600,000				447,600,000		482,000,000		155,200,000	292,400,000		292,400,000	482,000,000
Weighted-average interest cost, percentage									4.10%	5.90%		5.90%
Expected life of debt instrument									7 years			7 years
Interest rate percentage															3.50%	3.75%
Annual commitment fee payable, percentage															0.50%
Proceeds from borrowings					155,000,000	535,000,000													535,000,000
Payment of loan costs									4,100,000										16,400,000
Total assets	660,794,000				660,794,000		680,760,000	322,300,000
Restricted cash	18,600,000				18,600,000			18,600,000
Gain (loss) from early extinguishment of debt	(3,900,000)	(500,000)	(28,200,000)	5,200,000	(4,443,000)	(23,035,000)
Prepayment premium and write off of unamortized deferred loan fees			25,300,000
Repurchased of notes																					$ 62,500,000