Postretirement and Other Employee Benefits (Fair Value of Plan Assets) (Details) - USD ($) $ in Thousands	Aug. 31, 2020	Aug. 31, 2019	Aug. 31, 2018
Defined Benefit Plan Disclosure [Line Items]
Fair Value	$ 538,273	$ 158,101	$ 151,715
Asset Allocation (as a percent)	100.00%	100.00%
Cash and cash equivalents | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair Value	$ 14,900	$ 7,705
Asset Allocation (as a percent)	3.00%	5.00%
Global equity securities | Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair Value	$ 208,384	$ 20,215
Asset Allocation (as a percent)	38.00%	13.00%
Corporate bonds | Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair Value	$ 237,812	$ 42,522
Asset Allocation (as a percent)	44.00%	27.00%
Government bonds | Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair Value	$ 58,095	$ 69,880
Asset Allocation (as a percent)	11.00%	44.00%
Insurance contracts | Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair Value	$ 19,082	$ 17,779
Asset Allocation (as a percent)	4.00%	11.00%