CREDIT ARRANGEMENTS (Long-term Debt, Including the Deferred Gain from the Termination of the Interest Rate Swaps) (Details) - USD ($) $ in Thousands	May 31, 2018	Aug. 31, 2017	Jul. 31, 2017	May 31, 2013
Debt Instrument [Line Items]
Total debt	$ 1,171,138	$ 832,077
Less debt issuance costs	12,161	7,315
Total amounts outstanding	1,158,977	824,762
Less current maturities	19,874	19,182
Long-term debt	$ 1,139,103	805,580
2027 Notes
Debt Instrument [Line Items]
Weighted average interest rate	5.375%		5.375%
Total debt	$ 300,000	300,000
2026 Notes
Debt Instrument [Line Items]
Weighted average interest rate	5.75%
Total debt	$ 350,000	0
2023 Notes
Debt Instrument [Line Items]
Weighted average interest rate	4.875%			4.875%
Total debt	$ 330,000	330,000
Other, including equipment notes
Debt Instrument [Line Items]
Total debt	$ 46,763	52,077
Revolving credit facility | 2022 Term Loan
Debt Instrument [Line Items]
Weighted average interest rate	3.103%
Total debt	$ 144,375	$ 150,000