CREDIT ARRANGEMENTS (Long-term Debt) (Details) - USD ($) $ in Thousands	Aug. 31, 2021	May 31, 2021	Aug. 31, 2020	May 31, 2019
Debt Instrument [Line Items]
Total long-term debt including current maturities	$ 1,077,922		$ 1,092,266
Less debt issuance costs	8,141		8,581
Total amounts outstanding	1,069,781		1,083,685
Current maturities of long-term debt	54,366		18,149
Long-term debt	$ 1,015,415		1,065,536
2031 Notes
Debt Instrument [Line Items]
Weighted average interest rate	3.875%
Total long-term debt including current maturities	$ 300,000		0
Less debt issuance costs	$ 4,900
2027 Notes
Debt Instrument [Line Items]
Weighted average interest rate	5.375%
Total long-term debt including current maturities	$ 300,000		300,000
2026 Notes
Debt Instrument [Line Items]
Weighted average interest rate	5.75%	5.75%
Total long-term debt including current maturities	$ 0		350,000
Less debt issuance costs				$ 77,800
2023 Notes
Debt Instrument [Line Items]
Weighted average interest rate	4.875%
Total long-term debt including current maturities	$ 330,000		330,000
Other
Debt Instrument [Line Items]
Weighted average interest rate	5.10%
Total long-term debt including current maturities	$ 19,492		21,329
Short-term borrowings
Debt Instrument [Line Items]
Total long-term debt including current maturities	$ 26,560		0
Short-term borrowings | Poland Program
Debt Instrument [Line Items]
Weighted average interest rate	1.05%
Finance leases
Debt Instrument [Line Items]
Total long-term debt including current maturities	$ 52,144		50,224
Revolving credit agreement | Poland Term Loan
Debt Instrument [Line Items]
Weighted average interest rate	1.71%
Total long-term debt including current maturities	$ 49,726		$ 40,713