Commitments and Contingencies (Narrative) (Details) - USD ($) $ in Thousands	3 Months Ended
	Nov. 30, 2020	Aug. 31, 2020	Nov. 30, 2019
Commitments And Contingencies [Line Items]
Liabilities	$ 271,301	$ 272,008	$ 253,811
Lindsay, Nebraska Facility [Member]
Commitments And Contingencies [Line Items]
Current environmental remediation accrual	16,100
Liabilities	$ 11,000
Liabilities discounted risk Free interest rate	1.20%
Discounted portion of liabilities	$ 12,400
Lindsay, Nebraska Facility [Member] | General and Administrative Expense [Member]
Commitments And Contingencies [Line Items]
Liabilities		$ 1,000