Postretirement and Other Employee Benefits (Fair Value of Plan Assets) (Details) - USD ($) $ in Thousands	Aug. 31, 2018	Aug. 31, 2017	Aug. 31, 2016
Defined Benefit Plan Disclosure [Line Items]
Fair Value	$ 151,715	$ 146,698	$ 143,702
Asset Allocation (as a percent)	100.00%	100.00%
Cash and cash equivalents | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair Value	$ 6,682	$ 5,760
Asset Allocation (as a percent)	4.00%	4.00%
Global equity securities | Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair Value	$ 35,932	$ 41,971
Asset Allocation (as a percent)	24.00%	29.00%
Corporate bonds | Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair Value	$ 41,088	$ 41,987
Asset Allocation (as a percent)	27.00%	29.00%
Government bonds | Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair Value	$ 51,597	$ 41,738
Asset Allocation (as a percent)	34.00%	28.00%
Insurance contracts | Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair Value	$ 16,416	$ 15,242
Asset Allocation (as a percent)	11.00%	10.00%