Postretirement and Other Employee Benefits (Net Periodic Benefit Cost) (Details) - USD ($) $ in Thousands	12 Months Ended
	Aug. 31, 2020	Aug. 31, 2019	Aug. 31, 2018
Retirement Benefits [Abstract]
Service cost	$ 24,606	$ 1,437	$ 1,063
Interest cost	3,041	3,715	3,807
Expected long-term return on plan assets	(14,115)	(5,291)	(5,954)
Recognized actuarial (gain) loss	(4,159)	741	1,127
Amortization of prior service credit	(45)	(44)	(88)
Net settlement loss	230	634	116
Net periodic benefit cost	$ 9,558	$ 1,192	$ 71