CREDIT ARRANGEMENTS (Long-term Debt, Including the Deferred Gain from the Termination of the Interest Rate Swaps) (Details) - USD ($)	9 Months Ended	12 Months Ended
	May. 31, 2015	Aug. 31, 2014	May. 31, 2013	Aug. 31, 2008	Jul. 31, 2007
Debt Instrument [Line Items]
Total long-term debt including current maturities	$ 1,289,122,000	$ 1,289,047,000
Current maturities of long-term debt	9,753,000	8,005,000
Long-term debt	1,279,369,000	1,281,042,000
$400 million notes at 6.50% due July 2017
Debt Instrument [Line Items]
Debt instrument, face amount	$ 400,000,000	$ 400,000,000			$ 400,000,000
Debt instrument, interest rate, stated percentage	6.50%	6.50%			6.50%
Debt instrument, maturity date	July 2017	July 2017
Weighted average interest rate	5.74%
Total long-term debt including current maturities	$ 406,317,000	$ 408,546,000
$500 million notes at 7.35% due August 2018
Debt Instrument [Line Items]
Debt instrument, face amount	$ 500,000,000	$ 500,000,000		$ 500,000,000
Debt instrument, interest rate, stated percentage	7.35%	7.35%		7.35%
Debt instrument, maturity date	August 2018	August 2018
Weighted average interest rate	6.40%
Total long-term debt including current maturities	$ 514,837,000	$ 518,305,000
$330 million notes at 4.875% due May 2023
Debt Instrument [Line Items]
Debt instrument, face amount	$ 330,000,000	$ 330,000,000	$ 330,000,000
Debt instrument, interest rate, stated percentage	4.875%	4.875%	4.875%
Debt instrument, maturity date	May 15, 2023	May 15, 2023
Weighted average interest rate	4.875%
Total long-term debt including current maturities	$ 330,000,000	$ 330,000,000
Other, including equipment notes
Debt Instrument [Line Items]
Total long-term debt including current maturities	$ 37,968,000	$ 32,196,000