CREDIT ARRANGEMENTS (Narrative) (Details)	12 Months Ended
	Aug. 31, 2020 USD ($)	Aug. 31, 2019 USD ($)	Aug. 31, 2018 USD ($)	Aug. 31, 2020 PLN (zł)	May 31, 2020	Nov. 01, 2018 USD ($)	May 31, 2018 USD ($)	Jul. 31, 2017 USD ($)	May 31, 2013 USD ($)
Debt Instrument [Line Items]
Loss on debt extinguishment	$ (1,778,000)	$ 0	$ 0
Total long-term debt including current maturities	1,092,266,000	1,254,921,000
Interest costs capitalized	2,500,000	300,000	7,300,000
CMCP
Debt Instrument [Line Items]
Maximum borrowing capacity	74,600,000	69,000,000.0		zł 275,000,000.0
Revolving line of credit outstanding amount	0	0
Stand by letters of credit outstanding amount	800,000	1,100,000
Borrowings under uncommitted lines of credit	22,400,000	0	0
Repayments of uncommitted credit lines	22,400,000	0	$ 0
Revolving credit agreement
Debt Instrument [Line Items]
Maximum borrowing capacity	350,000,000.0
Revolving credit facility, maximum borrowing capacity	600,000,000.0
Revolving line of credit outstanding amount	$ 0	0
Minimum interest coverage ratio	2.50
Maximum debt to capitalization ratio	0.60
Actual interest coverage ratio	9.36			9.36
Actual debt to capitalization ratio	0.37			0.37
Stand-by letters of credit
Debt Instrument [Line Items]
Maximum borrowing capacity	$ 50,000,000.0
Stand by letters of credit outstanding amount	3,000,000.0	3,000,000.0
Short-term borrowings
Debt Instrument [Line Items]
Total long-term debt including current maturities	$ 0	3,929,000
2027 Notes
Debt Instrument [Line Items]
Term loan, maximum principal amount								$ 300,000,000.0
Weighted average interest rate	5.375%			5.375%				5.375%
Total long-term debt including current maturities	$ 300,000,000	300,000,000
2026 Notes
Debt Instrument [Line Items]
Term loan, maximum principal amount							$ 350,000,000.0
Weighted average interest rate	5.75%			5.75%	5.75%
Total long-term debt including current maturities	$ 350,000,000	350,000,000
2023 Notes
Debt Instrument [Line Items]
Term loan, maximum principal amount									$ 330,000,000.0
Weighted average interest rate	4.875%			4.875%					4.875%
Total long-term debt including current maturities	$ 330,000,000	330,000,000
Term Loan | Revolving credit agreement
Debt Instrument [Line Items]
Term loan, maximum principal amount						$ 180,000,000.0		$ 150,000,000.0
Weighted average interest rate	3.148%			3.148%
Loss on debt extinguishment	$ (1,800,000)
Total long-term debt including current maturities	0	210,125,000
Poland Term Loan | CMCP
Debt Instrument [Line Items]
Term loan, maximum principal amount	67,900,000			zł 250,000,000.0
Total long-term debt including current maturities	$ 40,700,000			zł 150,000,000.0
Poland Term Loan | Revolving credit agreement
Debt Instrument [Line Items]
Weighted average interest rate	1.73%			1.73%
Total long-term debt including current maturities	$ 40,713,000	0
U.S. Program
Debt Instrument [Line Items]
Transfer of Accounts Receivable Program, Face Amount	200,000,000.0
Transfers of Accounts Receivable Outstanding	0	0
Poland Program
Debt Instrument [Line Items]
Transfer of Accounts Receivable Program, Face Amount	59,700,000	55,200,000		zł 220,000,000.0
Transfers of Accounts Receivable Outstanding	$ 0	$ 3,900,000
Advance Limit as Percent of Eligible Trade Accounts Receivable Transferred	90.00%			90.00%
Poland Program | Short-term borrowings
Debt Instrument [Line Items]
Weighted average interest rate	0.98%			0.98%
U.S. Program with Consent of CMCRV and Program Administrative Agent
Debt Instrument [Line Items]
Transfer of Accounts Receivable Program, Face Amount	$ 300,000,000.0