Debt and Lines of Credit - Debt (Details) - USD ($)	Aug. 31, 2020	Aug. 31, 2019
Debt Instrument [Line Items]
Total debt	$ 401,100,000	$ 356,600,000
Long-term Debt, Fiscal Year Maturity [Abstract]
2021	24,300,000
2022	20,200,000
2023	355,300,000
2024	300,000
2025	300,000
After 2024	700,000
Senior Unsecured Notes \| Unsecured public notes due December 2019
Debt Instrument [Line Items]
Debt outstanding	0	350,000,000.0
Senior unsecured public notes due December 2019, unamortized discount and deferred costs	0	(100,000)
Unsecured Term Loan \| Borrowings under Term Loan Facility
Debt Instrument [Line Items]
Total debt	395,000,000.0	0
Industrial Revenue Bond \| Industrial revenue bond
Debt Instrument [Line Items]
Total debt	4,000,000.0	4,000,000.0
Bank loans \| Fixed-rate Bank Loans
Debt Instrument [Line Items]
Total debt	$ 2,100,000	$ 2,700,000

Amount, before unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but is not limited to, notes payable, bonds payable, commercial loans, mortgage loans, convertible debt, subordinated debt and other types of debt.

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